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this point of suspension through a vertical galvanometer. The shockreceiving part is placed underground to avoid the interference of winds or that of violent detonations, the metal block being set upon a wooden pile driven some distance in solid earth. When properly set, a single make and break contact of this kind is so sensitive that the impact of 3 pounds of stone, falling from a height of 5 ft. upon the ground, at a distance of 50 ft. from it, moved the needle of the galvanometer very determinately. The intervening ground was clay.

Coal-gas for Lighthouses.-Mr. J. Wigham recently gave a lecture in Dublin on this subject. He said that coal-gas was first used in lighthouses in 1865, by Mr. Samuel Bewley of the Irish Board of Lights, who tried some experiments at Howth. The first burner used was called the "crocus.” The principles involved in this burner, and the means taken to economise the gas, proved that by the crocus there was an immense saving, taking light for light, as compared with the gas usually used in our houses. The lecturer then alluded to the economy as compared with oil. There was a saving of about 50%. per annum on each lighthouse in which the gas had been tried, and, in the case of intermitting lights, the difference was much greater as regards economy. Dr. Tyndall has been sent down to investigate the whole matter at Howth, and that gentleman had reported favourably. There were five lighthouses at present on the Irish Coast illuminated by gas, and they are about to try it on two of the English lighthouses. In speaking of the electric light, Mr. Wigham said that though the latter was very intense, yet it was deficient in quantity, and it was not so good as coal-gas for penetrating fogs. Mr. Wigham then proceeded to explain the mechanical arrangements and the construction of the lenses.—Royal Dublin Society, March 18, 1872.

Estimating the Intensity of Light.-The Chemical News, April 12, quoting from an American journal, states that Dr. Vogel proposes nitroprussid iron as a suitable salt for determining quantitatively the intensity of light. For the preparation of this reagent, dissolve chemically pure oxide of iron, best obtained from the oxalate, in hydrochloric acid, and evaporate nearly to dryness to expel the excess of acid; and after filtering, add an aqueous solution of nitroprussidnatrium in proportion of three of the iron to two of the latter. There is usually a slight precipitate produced by this mixture, which can be collected on a filter; but this operation must be performed in a dark room. We have now a liquid excessively sensitive to the action of sunlight. By exposing a small quantity of a known specific gravity to the action of light, a precipitate of prussian-blue will instantly begin to fall; and, on redetermining the sp. gr. in the dark chamber, its decrease will be found to be proportional to the precipitate; and we have thus the data for measuring the intensity of light. It was found by Dr. Vogel that the liquid, exposed for forty-eight hours before a kerosene lamp, was not in the least affected, but a piece of magnesium wire, when burned, immediately produced a precipitate. By employing a long instrument graduated in millimetres, it would appear to be possible to measure the intensity of the light by the number of millimetres occupied by the precipitate. The invention has an important bearing upon photography.

How to bend Glass Tubes so as to fit Apparatus.-Mr. J. Laurence Smith

states that it is well known that it requires some tact to bend a tube with ́an even curve and without collapsing its sides, and many chemists never do succeed in bending them skilfully. Although having no particular skill in this matter, he never fails to bend them perfectly satisfactorily, by using a flame different from the one usually employed; the flame is one given by the Bunsen burner described in his article on alkali determination in silicates (see Chemical News, vol. xxiii., p. 235). The burner is very commonly used now in all laboratories, where the extremity of the burner is flattened out so as to give a short and thin but broad flame, something like the flame of an ordinary gas-burner. The tube is placed in this flame and turned round and round, until a good heat is given to the tube; it is then withdrawn from the flame and bent, when it does so with a perfect curve and no collapse of the sides of the tube. Of course this is only intended for the smaller tubes, but a tube of 1 centimetre and more can be thus bent very readily.

Spectra of Manganese in Blowpipe Beads.-Manganese may be easily detected in this manner according to Mr. Charles Horner (Chemical News, March 22). The following is the best way of preparing the beads and examining their spectra. Sufficient chlorate of potash should be volatilised in the loop of platinum wire to form a bead about the size of a pin's head, then take up the merest trace of the oxide and fuse it; next add enough chlorate to fill the loop, and very gently flame the bead for a few seconds and withdraw, when it crystallises a delicate pink colour. In adding the second portion of chlorate care must be observed not to volatilise the salt. and the best result is when the bead does not much exceed the thickness of the wire. If after adding the second portion we volatilise the chlorate, we immediately obtain a greenish-coloured bead of manganate of potash, and more transparent than the pink bead. In order to see the spectra of these beads, they should be examined by the spectrum microscope and strongly illuminated. The pink bead exhibits several absorption-bands more or less definite according to the amount of manganese present. The three most distinct bands, however, lie between D and b, and may be seen when the bead is scarcely coloured. This spectrum very closely resembles that given by the crystals of perchlorate coloured by permanganate of potash, but the bands are slightly more refrangible in the former. The green bead gives a spectrum of two bands, one broad band covering the sodium line, and a very narrow band in the orange ray. This spectrum test is most useful in the examination of minerals, for although the pink colour is sometimes disguised by the presence of other substances, as in rhodonite, which communicates a yellowish tint to the bead, yet the three principal absorption-bands are plainly visible.

ZOOLOGY AND COMPARATIVE ANATOMY.

Zoological Nomenclature. This subject has excited considerable attention in the United States. "Silliman's American Journal," May 1872, contains an important review of Mr. Lyman's recent and somewhat novel opinions on the subject. We of course cannot enter on so long a question. We may, however, refer the reader to Mr. Lyman's work, "Illustrated Catalogue of the

Museum of Comparative Zoology," in which, under the heading of "Notes on Nomenclature," his peculiar views are expressed. It is remarkable that some years ago, the American Association for the Advancement of Science appointed a committee to reconsider the canons of biological nomenclature, and to report whether, with the growth of science, they required any additions or alterations. No report has yet been made, nor, so far as we are aware, is any likely to be presented, until the subject is again brought prominently forward and new instructions given. Professor A. E. Verrill has since republished the Revised Rules of Zoological Nomenclature adopted by the British Association for the Advancement of Science in 1865, and has accompanied them by a few apt comments: in England, Mr. W. F. Kirby, in a paper read before the Linnean Society of London, has called attention to the extensive changes which a strict adherence to the laws of priority would cause in the generic nomenclature of butterflies; and quite recently has put the same into practice in his catalogue of these insects.

A New Crustacean: Tomocaris Peircei has been discovered by Professor Agassiz. This, which is named as above, was dredged in 45 fathoms about 40 miles east of Cape Frio. It is described as very like Serolis, with the marked difference, that the thoracic rings are much more numerous, and the abdomen much smaller; and it is said that its resemblance to Trilobites is unmistakable and very striking, and that it can be referred to no one of the orders or families in Milne Edwards' or Dana's classification. From the details of Prof. Agassiz's description, the animal is evidently one of the Serolidæ, apparently congeneric, perhaps specifically identical, with the Brongniartia trilobitoides of Eights (Trans. Albany Institute, vol. ii., p. 53, pl. 1, 2, 1833), which is referred to the genus Serolis by Audouin and Milne Edwards (Archives du Muséum d'Hist. nat., tome ii., p. 29, pl. 2, fig. 11, 1839), and retained in the same genus by Milne Edwards in his great work (Hist. nat. des Crust., tome iii., p. 232, 1840). To make this apparent it is necessary to observe that what Prof. Agassiz calls the head includes the first thoracic segment, which in the Serolida is anchylosed with the head; that what he considers the three posterior segments of the thorax, have been regarded by carcinologists as belonging to the abdomen; and that, as a result of this first homology, what have been regarded as the anterior legs are called maxillipeds. The only point in the whole description which can militate against the view here expressed is in the description of the nine pairs of legs which are said to be "all alike in structure; " the six anterior pairs, however, are "larger than the three last, which are also more approximated to each other," thus agreeing perfectly in position with the three anterior abdominal legs of the ordinary Serolidæ. The perfect agreement in all other respects, however, leaves little doubt of the close affinity between Tomocaris and the Brongniartia of Eights. It may be well to notice that among the species referred to Serolis, there are several genera, distinct from the typical S. paradoxa, and that the species described by Eights represents one of these, although the name Brongniartia is preoccupied.-Silliman's Journal, May.

The Great Public Aquarium at Naples.-An account of this immense undertaking is given by a contemporary, and is of sufficient interest to have a place in our columns. The building, which is under the

direction of M. Anton Dohrn, is rectangular, measuring 100 ft. by 70 ft., with a height of 40 ft., and is 100 ft. from the sea. The lower part is to be occupied by the tanks of the great aquarium, to be opened to the public; and the upper will contain 24 rooms for laboratories, a library and collections, with lodging rooms for three or four zoologists. There will be 53 tanks in the lower story, one of them 32 ft. long, 10 broad and 3 deep, another, 26 ft. long, and twenty-six 3 ft. by 3 ft. The tanks throughout are furnished with a continuous current of sea-water. Upstairs, the library room is large enough to hold 25,000 volumes. The principal laboratory room will contain 20 to 30 tanks of different sizes; and besides there are private laboratories for the chief zoologist and the first assistant, and other small laboratory rooms, and rooms for collections.

Three Additional Zoological Publications have lately made their appearance, and if we may judge from the first numbers and from the character of the editors, they are likely to commend success. The one, "Archives de Zoologie Expérimentale et Générale," issued by Professor Lacaze Duthiers, will take a high place among scientific periodicals, and is likely, in French zoological literature, to take the position which Siebold and Kölliker's "Zeitschrift" takes in Germany. Professor Lacaze Duthiers, so well known for his thorough researches upon the Invertebrates of the Mediterranean, contributes an introduction to the first number, stating the aims of the publication, and concludes the number by an elaborate article on the auditive capsules of Gasteropoda. The other original article of this number is written by Mr. Perrier, who has given us an excellent paper on the Natural History of a fresh-water worm (Deto) allied to Nais. This periodical, as well as the other "Journal de Zoologie," published under the auspices of Professor Gervais, both have notes and reviews on scientific works published in countries outside of France, a feature which thus far has received but little attention from French scientific journals. Holland, which already publishes so many scientific memoirs and periodicals of great excellence, adds a purely zoological archive to its list, edited by Professor Selenka. The first number contains a tolerably complete embryology of one of the naked Gasteropods by Selenka, and a long paper by C. K. Hoffman on the anatomy of Echinoderms; both these papers are excellently illustrated. Professor Selenka intends to issue his Niederländische Archiv für Zoölogie whenever sufficient material is at hand; he solicits articles either in German, French, or English.

Appearance of Colour in Fish kept in Alcohol.—Mr. Richard Bliss, writing in the "American Naturalist," April, states that a short time since while examining a number of alcoholic specimens of Cyprinoids from Ogden, Utah, collected by Mr. J. A. Allen last September for the Museum of Comparative Zoology, he noticed a species of Richardsonius distinguished by a bright vermilion spot on the abdomen. The size of the spot varied in different individuals: in some it was quite small, in others it extended from the base of the pectoral fin to the anal opening. Calling Mr. Allen's attention to this fact he stated, greatly to his surprise, that this colour was not present in the living fish when he caught them, but appeared after the fish had been in alcohol a short time. A dissection of one of these fishes showed Mr. Bliss that the colour was deposited in the areolar layer or derm, and was

therefore a true pigmentary colour. The only explanation he can offer to account for this peculiar appearance of colour is this:-It is well known that during the breeding season fishes frequently take on the most brilliant colours, which disappear when that season is past. It is not therefore improbable that this colour may have been one, at least, of the colours assumed by the fish during the reproductive period, and that the alcohol served in some way to bring out the colour thus abnormally. Whatever may have been the cause, the fact that colour can so appear in fishes will serve as a caution to ichthyologists when describing species from alcoholic specimens alone, lest they confound abnormal or seasonal colours with those that are permanent.

Parthenogenesis among Lepidoptera.-It seems that the Dutch naturalist, M. H. Weizenbergh, jun., has performed a series of experiments on this interesting subject, the insect placed under observation being Liparis dispar, and concludes that it is possible for at least three successive generations to be produced without access of the male to the female. The following are the results of his very careful experiments :-(1) August 1866, eggs laid by impregnated females; April 1867, caterpillars appear, and in July perfect butterflies. (2) August 1867, eggs laid by females of this year are without impregnation; April 1868, caterpillars appear, and in July perfect butterflies. (3) August 1868, eggs laid by females of this year without impregnation; April 1869, caterpillars appear, and in July perfect butterflies. (4) August 1869, eggs laid by the females of this year without impregnation; April 1870, no results, the eggs all dried up. The power of reproduction appeared to decrease year by year when impregnation was prevented. Similar results have been noticed in other butterflies, in bees, and notably in aphides.

An Error of Mr. Darwin's.—The "American Naturalist" (May 1872) states, that in the last edition of his "Origin of Species," Mr. Darwin misstates Hyatt and Cope's law of acceleration and retardation in the following language: "There is another possible mode of transition, namely, through the acceleration and retardation of the period of reproduction. This view has lately been insisted on by Prof. Cope and others in the United States. It is now known that some animals are capable of reproduction at a very early age, before they have acquired their perfect characters," &c. A writer, who signs himself "Z," states, that Prof. Cope and others have not insisted on the above propositions, which he imagines to be supported by very few facts. Their theory of acceleration and retardation states, that, while the period of reproductive maturity arrives at nearly the same age or period of the year in most individuals of a single sex and species, the portion of the developmental scale which they traverse in that time may vary much. That an addition to the series of changes traversed by the parent would require, in another generation, a more rapid growth in respect to the series in question, which is acceleration. A falling short of accomplishing that completeness would result from a slower growth, hence the process is termed retardation. Vast numbers of observed facts prove that this is the great law of variation, towards which little progress has yet been made by students who are yet chiefly occupied with the co-operative law of natural selection.

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