a series of independent figures, designed to show the degree of development attained by each type at any epoch relatively to other epochs. These charts and diagrams were thoroughly discussed; and the lecture closed with a few remarks on the genealogy of plants, illustrated by an arborescent figure showing one of the possible ways in which the present forms of plant-life may have been derived. LETTERS TO THE EDITOR. [Correspondents are requested to be as brief as possible. The writer's name is in all cases required as proof of good faith.] Intelligence of the crow. JAPAN is the birds' paradise, as fire-arms cannot be carried except by special permit. Though their punishment of criminals is sometimes extremely cruel, to shoot birds for sport or for scientific purposes would never enter the heads of this kind-hearted people. I noticed, in many parts of the country, that the crow felt a sense of security, meeting man boldly, conscious that he is a benefactor-and acknowledged as such-by killing injurious grubs, even though he collect a few grains of corn in the operation. He scorns to fly at your approach, and fears not a stick pointed at him, which he never takes for a gun. He is as familiar in Japan as he is shy in America and Europe. Another instance of this bird's intelligence came under my observation as I was walking among the crumbling arches of Caracalla's baths in Rome, in April, 1852. When near the walls, a stone nearly as large as my fist fell at my feet. Fearing a recurrence of what I supposed was an accident of perishing masonry, our party went farther toward the centre of the area. A second and a third fell near us; and, looking up, I saw some crows circling above our heads, one of which dropped a fourth from his claws. It seems that we had been strolling too near their nests in the walls; and they took this method to drive us away, a very effectual one, as a stone of that size, falling from the height of sixty feet, was an exceedingly dangerous missile, and perhaps only prevented from being fatal by the failure of the bird to make allowance for the impetus given by its own motion. The aim was accurate, and the, discharge right overhead; but, as both we and the bird were moving, it fortunately missed its mark. SAMUEL KNeeland. Paleolithic man in Ohio. In SCIENCE of April 13, p. 271, Professor Wright remarks that " no paleolithic implements have as yet been found [in Oliio], but they may be confidently looked for." It has seemed to me possible, from my own studies of the remains of paleolithic man in the valley of the Delaware River, that traces of his presence may only be found in those river valleys which lead directly to the Atlantic coast, and that paleolithic man was essentially a coast-ranger, and not a dweller in the interior of the continent. If we associate these early people with the seal and walrus rather than with the reindeer, and consider them essentially hunters of these amphibious mammals rather than of the latter, it is not incredible. I submit that they did not wander so far inland as Ohio, nor even so far as the eastern slope of the Alleghanies; and we need not be surprised if paleolithic implements, concerning which there can be no doubt whatever, for recent Indians made and used stone implements that are 'paleolithic' in character, -are not found in Ohio, or even in Pennsylvania west of the valley of the Susquehanna River. Unquestionable evidences of paleolithic man in America have been found in the valleys of the Connecticut, Delaware, and Susquehanna Rivers, and probable traces of the same people in the valleys of the Hudson, Potomac, and James Rivers. This is an extensive range of territory, and one not too limited as the probable area occupied by a primitive people. If we could accept without qualification the assertion occasionally made, that America's earliest race was pre-glacial, the difficulties that beset the study of paleolithic man would quickly vanish. I am disposed to believe it, upon theoretical grounds, but have met with no satisfactory demonstration that such was the case. In a recent lecture before the Franklin institute of Philadelphia, Prof. H. Carvill Lewis remarked, "That man existed before the glacial epoch has been inferred from certain facts, but not satisfactorily proven." Accepting the above conclusion, and coupling it with the assertion made by both Professors Wright and Lewis, that the melting of the great continental glacier occurred so recently as ten thousand years ago, we are compelled to crowd several momentous facts in American archeology into a comparatively brief space of time; and it becomes more probable that the fabricators of the implements found in postglacial gravels came from some transatlantic continental area, and had not wandered far inland when met by southern tribes, who drove them northward, exterminated or absorbed them. On the other hand, if the relationship of paleolithic man and the Eskimo is not problematical, and the latter is of American origin, then I submit that man was pre-glacial in America, was driven southward by the extension of the ice-sheet, and probably voluntarily retreated with it to more northern regions; and, if so, then in Ohio true paleolithic implements will surely be found, and evidences of man's pre-glacial age will ultimately be found in the onceglaciated areas of our continent. CHAS. C. ABBOTT. The copper-bearing rocks of Lake Superior. Mr. Selwyn's courteous reply in SCIENCE, No. 8, to my letter in No. 5, calls for only a few remarks from me. In his admission that I am right in asserting the existence of a great unconformity in the St. Croix region, between the basal sandstones of the Mississippi valley and the copper-bearing rocks, he yields the principal point for which I contend. It seems very unreasonable to me to extend the term 'Cambrian' over this unconformity; but, in the absence of any fossil evidence, I am relatively indifferent on this point. I only insist on the complete distinctness of the copper-bearing strata from the lowest sandstone of the Mississippi valley, and from the horizontal sandstone of the eastern end of the south shore of Lake Superior. Mr. Selwyn evidently does not appreciate that the St. Croix valley unconformity is not merely locally very great.' Our conclusions as to this unconformity are not based on any one local unconformable contact, but upon the fact, that, for a distance of over fifty miles in a north-westerly to south-easterly direction, the basal sandstone of the Mississippi valley lies horizontally athwart the courses of the tilted Keweenawan beds, overlying and burying the western termination of these beds, which are here disposed in synclinal form. Nor is the St. Croix Falls locality, described in the third volume of the Geology of Wisconsin, the only place in the St. Croix valley where the unconformity may be actually seen. Besides other places, it may be finely seen on Snake and Kettle rivers, in Minnesota, where the Keweenawan beds are identical in all respects, even to the occurrence of interbedded porphyry-conglomerates and cupriferous amygdaloids, with those of Keweenaw Point. As to the Animikie group, I have only to say, that I have not asserted its identity with the so-called Huronian rocks on the east shore of Lake Superior, spoken of by Mr. Selwyn, but merely its probable identity with the original Huronian of the north shore of Lake Huron, which neither I nor Mr. Selwyn have seen, and its certain identity with the ironbearing schists of the south shore of Lake Superior. The term 'Huronian' has been so differently used by different members of the Canadian geological corps since the first establishment of the system, that much doubt must still remain as to whether there are two sets of schistose rocks north of Lake Superior, or not. This much, however, I regard as certain; viz., that the flat-lying Animikie rocks of Thunder Bay and northern Minnesota were once continuous with some of the folded schists lying north of them in northern Minnesota and Canada, the Vermilion Lake iron-bearing schists, for instance, although now separated from them by belts of gneiss and granite. The lithological differences between the Animikie rocks and the folded schists are often more apparent than real; while, in many respects, there is a very close lithological likeness. However, I do not expect, and indeed have no right to expect, acquiescence in my novel position as to the Animikie rocks until the evidence I have collected has been published. I am confident, that, with the evidence that I now have, in his hands, Mr. Selwyn would at least think the matter worth looking into. With regard to the occurrence of volcanic ash in the Keweenaw series, I must acknowledge at once, that, so far as field-experience goes, Mr. Selwyn is far better equipped than I to judge of such materials, and that, not having seen Michipicoton Island, I am bound to accept his statement. I understood his first letter to indicate the occurrence of such ash in places which I had myself seen. Nevertheless, I bear in mind that a considerable school of English geologists has been long in the habit of calling almost any detrital rocks, not distinctly quartzose and associated with eruptive rocks, volcanic ash, when very often, at least, they might be simply derived by water-action from these rocks. Possibly there is some misunderstanding in our use of the term. Most of the detrital rocks of the Keweenaw series are volcanic detrital matter, in that they have been derived by wateraction from the eruptive, massive rocks of the same series; but I used the term as applied to fragmental material produced by the volcanic action itself. I do not know of any proof of such an origin in stratified material, other than the vesicular character, and perhaps constant angularity, of the particles, which proof I have failed to find. The discussion of such a question as the present one evidently cannot, however, be carried on satisfactorily in the pages of a journal; and I must ask my scientific confreres to defer their judgment until my publications on this subject, now in type, are issued. R. D. IRVING. University of Wisconsin, Pairing of the first-born. As regards the pairing of the first-born, my calculation of which called forth Mr. Hendricks's criticism, permit me to call attention to the following letter from Mr. Edmands, which I hope will set the matter straight. I applied to Mr. Edmands, because mathematics is not my fach; and I now have the pleasure of thanking him for the very kind attention he has given this matter. CHARLES SEDGWICK MINOT. Boston, April 24, 1883. As J. E. Hendricks remarks in SCIENCE of April 13, p. 278, "the chance that the first-born male will pair with the first-born female is as one to ten;" but Dr. Minot's argument in SCIENCE of March 16, p. 165, depends upon "the probability of both parents" being first-born, as stated at the beginning of the last paragraph on p. 165. If we first restrict the case to the offspring of first-born males, the chance that both parents will be first-born is evidently one in ten. But in the remaining ninety per cent of the race there would be no case of both parents being first-born. Taking the race as a whole, out of one hundred pairs, one pair would be both first-born, nine would have the male only first-born, nine the female only, and eighty-one (9X×9) neither male nor female first-born. This does not touch the question whether Dr. Minot is justified in giving no weight to the eighteen cases in a hundred, where only one individual of the pair is first-born. J. RAYNER EDMANDS. Cambridge, April 19, 1883. Place the ten females in a row, and the ten males opposite them, with the first-born' opposite each other. The ten males are susceptible of 1 X2 X3 X4 X5 X6 X 7 X 8 X 9 × 10 permutations, each of which furnishes a distinct system of pairing. Of these, 1 × 2 × 3 × 4× 5 × 6 × 7 × 8 × 9 are possible without disturbing the juxtaposition of the firstborn. The chance of their pairing will therefore be, 1 × 2 × 3 × 4 X5 X6 X 7 X 8 X 9 scientific genius live to a mature old age, will always be considered important ones. Maxwell was fortunate in possessing a father who early perceived the genius of his son, and directed his mind toward the study of mathematics and physics. He was also fortunate in springing from a race in which ability seemed to be hereditary. "The Clerks' for two centuries had been associated with all that was most distinguished in the northern kingdom, from Drummond of Hawthornden to Sir Walter Scott. John Clerk, the father of James Clerk Maxwell, the subject of the present sketch, succeeded to the property of Middlebie, which descended to him from his grandmother, Dorothea, Lady Clerk Maxwell, and assumed the name of Maxwell. It is related of him, that he took the greatest interest in science, especially in practical science. In a letter to his son, then at Cambridge, who proposed to spend the Easter holidays at Birmingham, he wrote, "View, if you can, armorers, gun-making and gun-proving, sword-making and proving, papier-maché and japanning, silver plating by cementation and rolling, ditto electrotype, Elkington's works, braziers' works by founding and by striking out in dies, turning, spinning teapot bodies in white metal, making buttons of sorts, steel pens, needles, pins, and any sorts of small articles which are cunningly done by subdivision of labor and by ingenious tools. Glass of sorts is among the works of the place, and all kinds of foundry-works, engine-making, tools and instruments, optical and [philosophical], both coarse and fine." His acme of festivity was to go with a boon friend to a meeting of the Edinburgh royal society. It is said by those who knew both parents, that the element of practicality entered very largely into their natures. The fine spirit of genius, the great imaginative powers, were not especially evident in them. Perhaps if the father had had the speculative mind of the son, he might have turned him toward philosophy and literature. The possession, in the father, of great interest in practical and useful processes, doubtless influenced the son's future. At an early age Maxwell showed that he inherited the curiosity of his father in regard to machines and the phenomena of nature. It is related, that, when he was two years and ten months old, "he has great works with doorlocks, keys, etc.; and Show me how it doos ' is never out of his mouth." Throughout his childhood his constant question was, 'What's the go o' that?' He was especially interested in colors. 'That (sand) stone is red; this (whin) stone is blue.' But how d'ye know it's blue?' His aunt, Miss Cay, was heard to remark "that it was humiliating to be asked so many questions one could not answer, by a child like that." The picture given of the boy's pursuits-his great activity of body and mind; his delight in nature's moods; his love for the deep brown of the brook, the shifting play of light on the foliage, the colors of the wandering clouds; his moods of lying on his back, watching the clouds, and wondering' shows the boy as father of the man. On stormy days he read voraciously every book within his reach, or spent his time in drawing, or inventing curious combinations of colors. The specimens of his early drawings show that he had an accurate eye, which might have made him an artist of fair talent. At the age of ten his tutor pronounced him slow to learn, probably judging him by old scholastic methods, which were ill fitted to bring out the child's tastes; and his father accordingly placed him at the academy in Edinburgh. Here the boy, who had been brought up apart from other boys, and had been accustomed to gang his own gate' with youthful fancies unridiculed by the average unpoetical schoolboy, was much persecuted at first by his school-fellows, who were amused by his singular clothes and broad accent. He gradually made a place for himself, however, and discovered that Latin was worth learning, and Greek very interesting. It is related that he took the foremost place in Scripture biography and in English. In arithmetic, as well as in Latin, his comparative want of readiness kept him down. At the age of thirteen he remarks in a letter, "I have made a tetrahedron and a dodecahedron, and two other hedrons whose names I don't know." At this time he had not begun geometry; yet he had discovered for himself the nature of the five regular solids, and had also constructed out of pasteboard other symmetrical polyhedra. His sense of humor is early apparent. In one of his letters, written at the age of eleven, he writes concerning his place in the class, "Talking about places, I am fourteen to-day, but I hope to get up. Ovid prophesies very well when the thing is over, but lately he has prophesied a victory which never came to pass." He enjoyed writing letters with curious illustrations drawn with pen on the margins, and subscribed himself Jas. Alex. McMerkwell, an anagram of his name. In one of these letters there is the first inkling of his poetic taste: "I made four lines of Latin one week. . . . But I am not going to try for the prize, as, when I lithp in numberth, it ith but a lithp, for the numberth do not come. But I am making English ones on the apparition of Creusa to Aeneas. "O father! can it be that souls sublime 66 The story of his school-years, told in his life, is of great interest to the American boy who has been fitted for college at the old Latin school in Boston, or at the ordinary American academy. Writing Latin verses was a marked feature of the academy at Edinburgh. This practice is comparatively unknown in our schools and academies. The present writer remembers that the subject of geometry was finished, so to speak, in the Boston Latin school in 1863, in about three months. In the Scottish academy the boy's mind was evidently allowed to rest upon the subject much longer, and he was stimulated to do problems of a more or less inventive kind. It was said of Maxwell at the age of fifteen, that, from " some mathematical principle, he would start off to a joke of Martinus Scriblerus, or to a quotation from Dryden, interspersing puns and other outrages on language of the wildest kind, humming and hawing in spite of P—; or, in a quieter mood, he would tell the story of Southey's Thalaba, or explain some new invention." This seems to show that the Scotch boy had a wider intellectual atmosphere around him than falls to the lot of the average American boy. But Maxwell, it may be remarked, was not an average Scottish boy. At the age of fourteen he gained the prize for English verse, for a poem on the death of the Douglas, and also the mathematical medal. At the age of fourteen he was much attracted to the subject of decorative painting, especially to the attempts of those who sought to reduce beauty in form and color to mathematical principles, and often discoursed upon the Greek patterns and on the forms of Etruscan urns. The consideration of this subject led him to contrive methods of drawing a perfect oval, and ovals in general. His father, who had watched his son's intellectual development with sympathetic interest, took his son's ovals to Professor James O. Forbes, of the University of Edinburgh, who thought that the simplicity and elegance of the boy's method entitled it to be brought before the Royal society. In the diary of the father we read, " M. 6. Royal society with James. Professor Forbes gave account of James's ovals. Met with very great attention and approbation generally." From this time the boy evidently studied geometry by the inventive method, to which the father of Mr. Herbert Spencer has deservedly called attention. Maxwell entered the University of Edinburgh at the age of sixteen. It is said of him at that time, that the originality and simplicity of his ways occasioned some concern to his conventional friends. He had a rooted objection to the vanities of starch and gloves. While at table he had an abstracted manner, as if occupied in studying the effects of refracted light in the glasses, or in devising some curious way of viewing objects. His aunt used to recall his attention by crying, 'Jamsie, you're in a prop' (mathematical proposition). His teachers had formed the highest opinion of his intellectual powers; and his companions enjoyed his quaint humor, and began to appreciate his high moral qualities, which were exemplified by his deep reverence for higher things, and his devotion to friends and to those who were suffering. Between the ages of sixteen and nineteen he studied at the University of Edinburgh. His studies were multifarious; but he was especially interested in polarized light, the stereoscope, galvanism, rolling curves, and the comparison of solids. His paper on rolling curves was presented to the Edinburgh Royal society, Feb. 19, 1849, by Professor Kelland; for it was not thought proper for a boy in a round jacket to mount the rostrum there." A paper on the equilibrium of elastic solids was also presented in the spring of 1850. It is related of him at this time, that he was regarded as a discoverer in natural philosophy, and a very original worker in mathematics. He is said to have felt the importance of cultivating the senses, and to have regarded dulness in that respect as a bad sign in any man. It is curious to notice, that he took great interest in the lectures of Sir William Hamilton on metaphysics. The views of the latter on the inferiority of the study of mathematics as a means of discipline to the study of philosophy and the classics, apparently did not diminish Maxwell's interest in the lecturer. The editor of the life of Maxwell remarks, in regard to Maxwell's interest in the lectures of Hamilton, "This is perhaps the most striking example of the effect produced by Sir William Hamilton on powerful young minds,—an effect which, unless the best metaphysicians of the subsequent age are mistaken, must be out of all proportion to the independent value of his philosophy." It is a noticeable peculiarity of great mathematicians, that their latter years are much given to metaphysics. With Maxwell, however, the reverse was true. While at the University of Edinburgh, he seemed to be as much attracted toward the study of metaphysics as toward mathematics, but hardly as much as to physics. As he grew older, the study of physics seemed to him more fruitful than that of mental philosophy. His method of studying mathematics is often alluded to in his letters. Thus, in a letter to a friend, written at the age of sixteen, he says, "I read Newton's Fluxions in a sort of way, to know what I am about in doing a prop. There is no time of reading a book better than when you need it, and when you are on the point of finding it out for yourself, if you were able." Again, in another letter, in speaking of the division of his time: "Then I do props, chiefly on rolling curves, on which subject I have got a great problem divided into orders, genera, species, varieties, etc." He continually talks of doing' props,' and apparently had a number upon which his mind was continually exercised. Nor was his method of studying physics less suggestive. In a letter dated Glenlair, July 5, 6, 1848, we read, "I have regularly set up shop now, above the wash-house at the gate, in a garret. I have an old door set on two barrels and two chairs, of which one is safe, and a skylight above, which will slide up and down. On the door (or table) there is a lot of bowls, jugs, plates, jam-pigs (jars), etc., containing water, salt, soda, sulphuric acid, blue vitriol, plumbago ore, also broken glass, iron and copper wire, copper and zinc plate, beeswax, sealing-wax, clay, rosin, charcoal, a lens, a Smee's galvanic apparatus, and a countless variety of little beetles, spiders, and wood-lice, which fall into the different liquids, and poison themselves. . . . I am making copper seals, with the device of a beetle. First I thought a beetle was a good conductor: so I embedded one in wax (not at all cruel, because I slew him in boiling water, in which he never kicked), leaving his back out; but he would not do. Then I took a cast of him in sealing-wax, and pressed wax into the hollow, and black-leaded it with a brush; but neither would that do. So at last I took my fingers and rubbed it, which I find the best way to use the black lead. Then it coppered famously. I melt out the wax with a lens, that being the cleanest way of getting a strong heat: so I do most things with it that need heat." He was busy at this age with experiments on polarized light and on colors. I have got plenty of unannealed glass of different shapes; for I find window-glass will do very well, made up in bundles. I cut out triangles, squares, etc., with a diamond, about eight or nine of a kind, and take them to the kitchen, and put them on a piece of iron in the fire one by one. When the bit is red-hot, I drop it into a plate of iron sparks to cool; and so on till all are done." He The years he spent in the University of Edinburgh were full of what might be called original work. He studied under Professor Forbes and Professor Kelland, and worked, "without any assistance or supervision, with physical and chemical apparatus." In 1850 he left Edinburgh for Peterhouse college, Cambridge, and, after a short residence in this college, left it for Trinity, in the expectation that the larger college would afford him ampler opportunities for self-improvement. His tutor says of him in 1853, It appears impossible for Maxwell to think incorrectly on physical subjects." He looked upon him as a great genius, with all its eccentricities, and prophesied that one day he would shine as a light in physical science. This impression was shared, apparently, by students who were the friends of Maxwell. seemed at this period to be in great spirits, and to thoroughly enjoy his college-life. At no time a narrow specialist, he opened his mind, while at Cambridge, to all the intellectual influences of the place. He became one of the club known as the Apostles.' He sought the society of classical men as well as that of the mathematicians. His progress at the university was watched by his father with keen and sympathetic interest. In a letter he writes, "Explain the pendulum experiment to me. You used often to speak of the retardation of the rotation of the earth by the friction of the tides. What is the phosphate of lime theory of mental progress?" And again: "Do you like the trig. lectures A? Tacitus is not new to you. His style must be congenial to a deep, half-sentence lecturer. You seem to have great gayeties with college parties with scientific dons. Do you take note of Stokes's experiments on the bands of the spectrum? Will they be suitable for repetition in the garret of the old house?" 6 The intimacy of the father and son, touched upon here and there in the life of the son, was a beautiful one. Maxwell's nature was capable of great devotion, and his feelings were exquisitely sensitive to kindness. His love for animals was but one expression of this abundant humanity. The editor of his life says, "In the autumn of 1850 the neighboring estate of Upper Corsock had been let to a shootingparty, one of whom remarked to me, what a pity it was that young Mr. Clerk Maxwell was so little suited for a country life.' I clearly recollect his look of exulting mirth when this |