-P. Wormleyi, 52.*-P. obtusatum, 56.+-P. Sciotoensis, 40.+Synedra radians, var.? a common fresh water species in this vicinity, has on the hoop about 75 striæ in the 001", very difficult, when balsam mounted, to resolve, owing probably to their shallowness.-Grammatophora subtilissima, 70 to 75 on the Greenport variety, 75 to 82 on the Providence variety.-Hyalodiscus Californicus: a large valve 005" in diameter (the central disc or umbilicus measuring 0016") gave at the margin of the umbilicus about 65 straight radial lines in 001"; midway be. tween that point and the circumference of the valve near 70 in 001"; and at the circumference about 75 in 001". More or less of these lines from the margin of the umbilicus, before reaching the circumference, bifurcate: this accounts for their being coarser near the umbilicus than at the circumference, as is shown by the above measurements, and by the greater ease with which they are resolved near the former point. The umbilicus itself is rayed, and in certain portions of the light exhibits curved lines.

To those interested in these matters it may not be unacceptable to state the means and method by which the above measurements were obtained. The objectives used were twoths, one by Spencer, the other by Ross, and ath by Powell and Lealand, upon one of Smith and Beck's first-class stands, with their second eye-piece and Jackson micrometer. An important adjunct to the above was Tolles' amplifier which consists essentially of an achromatic meniscus lens placed between the objective and the eye-piece, affording an amplification much superior to that from ordinary eye-piecing. The value of the Jackson micrometer (a scale of 005") with each of the objectives was carefully established by the averages of numerous trials on two of Smith and Beck's stage scales of 001". Thus the smallest divisions of the Jackson micrometer were made by moderate

* PLEUROSIGMA WORMLEYI, Sulliv.-Lanceolatum, conspicue sigmoideum, in apices acutos subito attenuatum; long. 003"; striis trans. et long. 52 in '001".

Fresh water; Columbus, Ohio, Prof. T. G. Wormley; Genessee river, N. Y., Mr. C. A. Spencer.

Resembles P. Spencerii, but is a smaller species, more evidently sigmoid and with rather abruptly attenuated ends: its striæ are more difficult to resolve, being shallower: texture of the valves thinner.

PLEUROSIGMA OBTUSATUM, sp. nov.-Oblongo-lanceolatum, leviter sigmoideum, apicibus obtusis; long. 0025"; striis trans. et long. 56 in 001".

Fresh water; Columbus, Ohio: Gambier, O., Prof. H. L. Smith; Genessee river, Mr. C. A. Spencer.

A very small species remarkable for the obtuse ends. It may be a Colletonema, but we have not observed it in gelatinous envelopes.

PLEUROSIGMA SCIOTOENSIS, sp. nov.-Lineare, modice sigmoideum, in apices obtusiusculos sensim attenuatum; long. 005"; striis trans. et long. 40 in 001". Fresh water; Columbus, Ohio: Genessee river, N. Y., Mr. C. A. Spencer. Not unlike P. Spencerii, for which it has passed as a variety, but is a larger species, its valve having more parallel sides and less acute ends. Its striation at once distinguishes it. Dry valve pale straw-color.

draws of the draw-tube to measure with different objectives from 000025" to 00000167" under an amplification of 1700 to 3600 times; precautions being taken against any disturbance of said value, that might arise from the thin glass covering the object. A Powell and Lealand cobweb micrometer was occasionally used, but mostly for corroboration. The Jackson micrometer, upon the whole, was found to be more manageable and satisfactory, the shortness of its lines permitting their coincidence with the striæ to be more readily observed. The light employed was sunlight, admitted through a small aperture into a darkened room with no other light could the striae of the highest marked frustules be distinctly resolved under an amplification sufficient for counting. In order to diminish as much as possible the chances of error, the counting always embraced as many contiguous striæ as covered a space equal, at least, to that between the centres of the five-lines of the micrometer, and when practicable a larger number was counted.

In conclusion, we may remark that our experiments are confirmatory of the generally received opinion that striæ closer than about 85 in 001" have not yet been resolved. Whether this limit is interposed by the physical properties of light, or whether it arises from defects still existing in our apparently faultless instruments, remains to be determined.

Columbus, Ohio, January 18th, 1859.

ART. XXXI.-Correspondence of Prof. Jerome Nicklès, dated Paris, January 3rd, 1859.

On the nature of simple bodies.-The Comptes Rendus for December contains a long memoir by Despretz on his researches to ascertain whether certain of the so-called elements are decomposable. His laborious and careful investigations have led to no decomposition, and he announces the conclusion that the substances called elementary are really elementary or incapable of decomposition. The author should have added, that they were not decomposable by the methods he used, for it is not probable that there is nothing more to be done in this branch of research. His process consists in submitting the element-cadmium for example-to the physical and chemical reagents ordinarily employed in analysis. He transforms it into an oxyd, then into salts of all kinds, decomposes these salts by chemical and galvanic methods, precipitates the metal at one time at the positive pole, at another at the negative, examines the crystalline form, turns it again into salts, which he decomposes, vaporizes the metal by means of the pile; and thus causes an element to pass through a great number of different states, and still arrives at the same element. While rendering justice to the zeal and patience of Mr. Despretz, we have to regret that these good qualities have been here wasted,

for the researches would be a hindrance to the progress of science if taken seriously.

Dumas took upon himself the refutation of Mr. Despretz, and brought to the subject his well known ability. He prefaced his remarks by presenting the following table which exhibits an interesting relation between the equivalents of certain simple and compound bodies.

Fl 19 Cl 35.5 Br 80 I 127 Difference 5.

N 14 Ph 31

Ca 20

As 75

Sr 43.75

S 16 Se 39.75
Methylamine 32
Ethylium 29

Sb 122

Ba 68-5 Pb 103.5

Te 645 Os 99.5 Difference 4.
Propylamine 60, etc. Diff. 3.
Butylium 57, etc.

Ethylamine 46
Propylium 43

}

Mg 12.25 0 8 Ammonium 18 Methylium 15 As this relation suggests a doubt as to the elements being simple, Dumas took occasion to express his opinion on this important question. Since the radicals (elements) in mineral chemistry present the same general relations as those in organic, he believes there is reason for bringing the two branches more closely together than is usually done. We can decompose the latter, and there is no proof that we may not decompose the former. The following are the conclusions in his memoir which will soon be published.

(1.) The compounds which the three kingdoms offer for our study, are reduced by analysis to a certain number of radicals which may be grouped in natural families. (2.) The characters of these families show incontestible analogies. (3.) But the radicals of mineral chemistry differ from the others in this, that if they are compound, they have a degree of stability so great that no known forces are capable of producing decomposition. (4.) The analogy authorizes the enquiry whether the former may not be compound as well as the latter. (5.) It is necessary to add that the analogy gives us no light as to the means of causing this decomposition, and if ever to be realized, it will be by methods or forces yet unsuspected.

Spontaneous generation,-Mr. Pouchet, Professor of Zoology at Rouen, is a decided believer in spontaneous generation, and has undertaken to revive this theory which has been overturned by the experiments of Schultze and Schwann, as well also by those of Messrs. Schroeder and Dusch. The former have shown that animal substances do not ferment when they are enclosed in air which has previously traversed a red hot tube. The latter state that these same substances may be preserved indefinitely in air which has previously been made to pass through a tube containing cotton. They have alike concluded from their experiments that fermentation and putrefaction are only the results of the life of certain inferior animalcules whose germs were in the atmosphere, and which are developed at the expense of the fermentible substance. Remove these germs either by filtration or calcination and there is no fermentation or putrefaction.

The mechanical theory of Liebig, which has at least as much probability in its favor as the physiological just mentioned, opens a way of explanation independent both of this and spontaneous generation.

The work of Mr. Pouchet was some time since announced, and the great success of the naturalist of Rouen proclaimed. It was stated that

SECOND SERIES, VOL. XXVII, No. 80.-MARCH, 1869.

he would surprise the scientific world with a prodigious number of experiments directly opposed to all received ideas.

The following are the results announced. He has seen cryptogams and animalcules to be produced in vessels when every organic germ has been previously destroyed and when the air had been washed in sulphuric acid or had traversed a tube of porcelain heated to a red heat. He has even succeeded in developing organic beings in artificial air and also in pure oxygen.

The details of one of his experiments are as follows. A flask, holding a litre, was filled with boiling water, then hermetically sealed with the greatest precaution, then inverted in a mercury trough; then when the water is cold, it was opened under the mercury and half a litre of pure oxygen introduced. Immediately after was added to it, under the mercury, a small box of hay weighing 10 grams, which had just been raised, in a flask, by means of a stove to a temperature of 100° C. and kept at this temperature for 30 minutes. The flask was then hermetically sealed by the aid of its stopper ground with emery; and to make it sure, when taken from the mercury a coat of varnish and vermilion was put over the aperture.

Eight days afterward, small globules were found in the liquid and on the hay. On opening the flask at the end of ten days, the oxygen appeared to have remained pure. The whitish globules were due to a fungus in tufts which Mr. Montagne, the micrographer, called Aspergillus Pouchetii.

A plant is thus developed in a medium from which it was endeavored to exclude every species of organic germ; but the conclusion of Mr. Pouchet is quite too general, as no facts prove that every kind of vitality was destroyed during the exposure of the hay for 30 minutes to 100° C.

Ozonometry in the Crimea.-During the Crimean war, the French army physicians, established three observatories for ozonometric, thermometric and other meteorological observations, morning and evening each day, and also for keeping statistics of diseases and deaths. Dr. Berigny of Versailles has in charge a reduction of the observations, and the following are his conclusions on the subject of ozone.

(1.) The more the ozonometric test papers were colored in the open air, the more numerous were the sick that were taken to each of the hospitals. One of these hospitals was situated at the general quarters at Sebastopol (Observatory No. 1), the second at the south border of the Inkerman plateau (Obs. No. 2).

(2.) The higher the temperature the smaller the number of sick entered and also of deaths.

(3.) At the three observatories, the ozone curve was essentially the same; and (4.) the same was true for the temperature.

(5.) At observatory No. 1, the less the ozone, the greater the number of deaths, whilst at observatory No. 2 it was the reverse.

This is almost the only positive result which science and humanity have derived from that destructive war, which has cost so much money and so many lives.

Dynamoscopy.-Dynamoscopy is a new mode of auscultation, directed towards the examination of sounds hitherto not studied. The author,

Dr. Collongues, examines these sounds in case of a deceased person with an instrument with one extremity on the part to be ausculted and the other at the ear. It is with this instrument that Dr. Collongues supposes he is able to detect the evidence of actual death.

He found this evidence in 1854 in the case of a woman attacked with cholera who was not believed to be dead. Examining about the heart with his dynamoscope, he distinguished a crackling sound which continued even to the tenth hour after death. He followed up this trial with others, and has arrived at the following conclusions respecting this sound.

(1.) After the respiration and the beating of the heart have ceased at death, a crackling sound may be heard which he calls "bourdonnement." (2.) The sound continues from five to ten hours after death.

(3.) It goes on decreasing from the time of death, and is last perceived about the præcordial and epigastric regions.

The results have been confirmed by observations on animals. It hence results that life continues until the cessation of this sound has ceased, and the cessation is a positive sign of death. This observation offers a means of distinguishing lethargy from death, as the sound does not cease in lethargy.

On applying the instrument to the extremity of the fingers, a sound of similar kind is heard which varies with the age, sex, state of health, activity or repose. The crackling is more rapid in children than in adults, and still more so than in aged persons. It is more gentle in woman than in man of the same age, and the crackling sounds ("pétillemens") are in general twice as numerous as those of man. There is also a great difference for different temperaments, and for different seasons and climates.

A singular experiment made with the instrument is to hear a faint and agreeable harmony which is made at the extremity of the fingers of a man asleep, whilst when awake there is only a great discordance in the "bourdonnement." Dr. Collongues supposes that these sounds have their seat in the nerves.

Artificial Caoutchouc.-This substance is obtained by the action of chlorid of sulphur on oils. On adding to oils an excess of this chlorid, they become heated and take a consistence more or less viscous; after some days they harden and become friable. With one part of the chlorid to nine of the oil, there is a lively reaction, chlorhydric acid is disengaged, and it is all changed into an elastic substance like sponge which whitens in the water. The products are insoluble in water, alcohol, ether, oils, and sulphuret of carbon; they are attacked neither by ammonia nor by dilute acids, and are not altered at 150° C.

These facts have been recently communicated to the French Academy and they were regarded as new. They were known by myself in 1848, and the following is a brief statement of the remarks which I have made on the subject to the Academy. "In order to protect the glass stopper of a flask containing chlorid of sulphur from incrustation, I put on it a little oil. I was not a little surprised on the next day to find the coating completely solidified. I soon recognized that the solidification had been caused by the chlorid, and that in general, this compound hardened fatty bodies by modifying them more less. Being then engaged in other