i8 



NA TURE 



[May 7, 1908 



^ 



OUR ASTRONOMICAL COLUMN. 

 Daniel's Comet, i9o7d. — Signer Pio Emanuelli, of 

 Rome, has favoured us with a manuscript copy of a daily 

 ephemeris for Daniel's comet, calculated by him from the 

 elemeni? computed by Prof. E. MiUosevich. An abstract 

 from Jilj ephemeris is given below : — 



Ephemens nh. [^yLT. Paris). 



1900 a (igoS'o) O(i9o3"o) r A 



h. m. 



May 8 ... 14 7-6 ... -ocrr ... 0-590 ... 0467 



16 ... 14 1-4 ... -o 31-0 ... o 6jo ... 0-487 



24 ... :3 56-2 ... -o iS-8 ... 0-610 ... 0-508 



31 ... 13 52-6 ... -o 14-5 



From this it will be seen that the comet is now 

 apparently travelling very slowly through the constellation 

 Virgo in an easterly direction ; its present magnitude is 

 about ii-o, and it crosses the meridian about 11 p.m. 



The Solar Rotation determined from Hydrogen 

 Phenomena. — From a discussion of the results obtained in 

 a spectrograph ic determination of the solar rotation, using 

 the hydrogen lines Ha, H7, and H5, Prof. W. S. Adams 

 arrives at conclusions fundamentally important in any 

 study of the solar structure ; the full discussion, together 

 with a description of the instrument and methods employed, 

 appears in No. 3, vol. x.xvii., of the .istrophysical Journal 

 (.April, pp. 213 et scq.). 



The first conclusion is that the sun's rotational velocity 

 as shown by the hydrogen lines is higher than that given 

 by those of other elements and by the study of sun-spots 

 and faculjp : the excess amounts to 1° in the angular 

 motion at the equator. It is worthy of remark that Ha, 

 which shows abnormal tendencies in its width, its intensity, 

 and its behaviour at the sun's limb, giv^s slightly higher 

 velocities than the other hydrogen lines. The second con- 

 clusion is that in the regions w^here the hydrogen lines are 

 produced the equatorial acceleration of the solar atmo- 

 sphere is non-existent, or too small to be measured by the 

 present method. These conclusions point to the absorbing 

 hydrog-en being situated at a higher level than other 

 absorbing media, e.g. calcium ; a previous investigation 

 (see Nature, No. 1990, p. 158, December 19, 1907) showed 

 that carbon and lanthanum gave lower velocities than 

 general, and are, therefore, probably situated at a lower 

 level. 



The results of a study of the solar rotation, based on the 

 measurements of hydrogen flocculi, are published by Prof. 

 Hale in the same journal, and they confirm the absence 

 of the equatorial acceleration in the absorbing hydrogen 

 atmosphere of the sun. 



The Canals and Oases of Mars. — In the Century 

 Magazine for May (vol. Ixxvi., No. i, p. 127), Prof. Lowell 

 continues his explanation and discussion of Martian 

 features, taking the canals and oases as the special subjects 

 of this article. 



Recounting the history of the canaliform marking since 

 their discovery by Schiaparelli in 1877, Prof. Lowell 

 strongly emphasises the numerous points which go to prove 

 their actual reality. The narrowest canal appears as it 

 •would were it but three miles across, but the average 

 width is some twenty miles. They vary in length from 

 250 to 2500 miles, and one, the Eumenides Orcus, extends 

 for some 3450 miles. Schiaparelli mapped 113, but 436 

 canals are now known to the Flagstaff observers. Of the 

 oases, first seen by Prof. W. H. Pickering in 1892, there 

 are now 1S6 marked on the Flagstaff map of Mars. The 

 special features of all these markings, their seasonal varia- 

 tions, their similarities and concordant behaviour, and the 

 ■weight of evidence added bv the geminated canals, are 

 all discussed by Prof. Lowell, and the results are shown 

 to be consistent with the theory that the features are there 

 for a set purpose, their functions having been determined 

 ty sentient beings for the sustenance of life and vegetation 

 on a planet which has reached a stage further in the 

 evolutionary process than has the earth. 



The Colour Sensibility of Selenium Cells. — In a 

 recent determination of the moon's light, Messrs. |oel 

 Stebbins and J. C. Brown, of the Illinois University 

 Observatory, found that the results depended upon the ceil 



NO. 2010, VOL. 78] 



used, and suggested that the variation was due to differ- 

 ences between the colour-sensibility curves of the several 

 cells (see Nature, January 16 and 30, pp. 258 and 302). 

 In a recent investigation Mr. Stebbins found that this 

 explanation is correct, and in No. 3, vol. xxvii., of the 

 Astrophysical Journal (April, p. 183) he gives the numerical 

 results and a series of colour curves illustrating the varia- 

 tions of the four cells employed. 



The Astronomical Society of Antwerp. — The third 

 annual report (1907) shows that this society is progressive, 

 and is fulfilling its primary purpose, the popularisation of 

 astronomical science, exceedingly well. The instrumental 

 equipment has been largely added to, the various meetings 

 for practical work and for lectures are well attended, and 

 there are now about 140 names on the list of members. 

 An important event in the history of the society during the 

 past year was the foundation of the Gazette astronomique, 

 a most useful monthly journal for amateur observers. 



MICROGRAPHIC STUDY OF LEATHER. 



rjNDER the title "Etude micrographique du Cuir," 

 ^ M. Henri Boulanger has published in the Bulletin 

 de la Societe d'Encouragement for February of this year 

 a series of interesting drawings showing the microscopic 

 appearance of various sections of raw and tanned hide. 

 '1 he chief interest in these consists in the demonstration 

 of the changes which take place in the skin during the 

 process of tanning. About thirty years ago a very similar 

 study was undertaken by the late Franz Kathreiner, of 

 Worms, on the microscopic preparations of raw and tanned 

 calf skin, in all the various stages of the tanning process, 

 and the writer has had the privilege of seeing these very 

 beautifid preparations; unfortunately, Kathreiner's results 

 were never published. 



The microscopic appearance of sections of raw skin is 

 well known to those who have made a scientific study of 

 tanning, but that of leather has not received so much 

 attention owing to the difficulty of preparing sufficiently 

 thin sections to be of use, and further of differentiating 

 the constituent parts. 



The author himself remarks that it is almost impossible 

 to make a satisfactory section of the flesh side, and he 

 has therefore confined his studies e.xclusively to the 

 " grain " side of the skin. This is commonly called the 

 epidermis, but it is difficult to apply strictly the vocabulary 

 of the histologist ; in this case the true epidermis disappears 

 completely in the process of preparing the skins for 

 tanning, and what the tanner calls the " grain " of the 

 skins is the hyaline membrane covering the upper surface 

 of the Rete Malpighi. 



M. I?oulanger's method of preparing the sections of raw 

 skin has the advantage of being a rapid one ; small pieces 

 of skin are soaked for twelve hours in a solution com- 

 posed of ; — distilled water, 5 grams ; glycerin, 5 grams ; 

 acetone, 90 grams. They are then allowed to dry, embedded 

 in hard paraffin, and are ready for the microtome. The 

 staining and mounting of the sections is carried out by 

 the usual methods. The microscopic appearance of the 

 sections was reproduced by coloured drawings made with 

 the camera lucida, since a photograph will not show the 

 various depths of the section. The illustrations shown are 

 photographs of these drawings. Fig. i shows the appear- 

 ance of a si-ction of the grain side of a fresh cow-hide 

 taken from the breast between the fore legs; in scientific 

 language, the upper surface of the dermis — the fibro- 

 elastic layer. It is stained with carmine alum, and shows 

 clearly the flat, inert cells of the epidermis, which it is 

 often difllcult to preserve intact in microscopic sections, 

 especially in a hide or skin which has been salted. 

 Immediately below this are the living cells of the 

 Malpighian layer ; the nuclei of these cells are well shown 

 in the figure. Just below this layer, which will eventually 

 form the " grain " of the tanned leather, are seen the 

 papillc-e of the dermis ; the dark spots are the nuclei of 

 the cells of the connective tissue. A hair follicle is also 

 shown, as well as a hair in vertical section. The magnifi- 

 cation of the plate in the memoir is 2S5 diameters, and is 

 one-half this amount in the accompanying reoroductions 

 of two figures. Compare the appearance of Fig. i with 



