SCIENCE. 



411 



swim about. They measured 5./'8 to 8f (.00022 to .00033- 

 inch in diameter). After a while they become attached 

 to some object, lose their flagella, elongate and subdivide, 

 forming new growths of Ulothrix. — The American 

 Monthly Microscopical Journal. 



SELENOGRAPHICAL. 



For the purpose of comparing drawings of lunar 

 objects, it is proposed to circulate at frequent intervals, 

 among observers, a portfolio containing sketches and 

 descriptions of various formations, which will ultimately 

 be presented to the Selenographical Society. To cover 

 expenses, an annual subscription of 2s. 6d. will be re- 

 quired. Among those who have already signified their 

 intention of joining in the movement are Rev. F. B. 

 Allison, Mr. W. R. Birt, Mr. T. P. Gray, Rev. R. S. Hutch- 

 ings, and the Rev. Dr. Richards. Those who are willing 

 to add their names to the above list are requested to 

 communicate with the editor of " SCIENCE." 



BOOKS_RECEIVED. 



Sea Mosses. A Collector's Guide and an Introduction 

 to the Study of Marine Algae, by A. B. Hervey, 

 A.M. S. E. Cassino, Boston, 1881. 



We welcome this excellent book, published at a season- 

 able moment, which will make it doubly appreciated by 

 the public. 



To the thousands who are now making a temporary 

 home within the sound of the surf and who love the sea, 

 seeking its presence for rest of spirit or health of body, 

 the present work will be found a welcome companion 

 and guide, opening up a new channel for the pleasant 

 passage of leisure hours. No longer need the idler 

 watch the incoming and outgoing of the tides with list- 

 less indifference, or be weary of the beating of sleepless 

 waves, as they go tumbling among the rocks. 



The author prepares the way for another pleasure 

 which " this great and wide sea " can give us, besides 

 that which she offers to our fancy and our dreams. In 

 the contemplation and study of the exquisitely beautiful 

 flora which she nurtures in her ample waters. 



If you become acquainted with these plants, their 

 beauty, delicacy and grace, and know their names, 

 habits and history, you will admit the sea has added a 

 new charm to your existence. 



There may be no royal road to knowledge, but Mr. A. 

 B. Hervey has certainly selected the shortest, and most 

 agreeable path by which the tyro may acquire a practical 

 knowledge of the department of Cryptogamic Botany, in- 

 cluded in the study of the most beautiful of Marine Algae, 

 the Sea Mosses. 



The publishers have done justice to Mr. Hervey 's work, 

 and have produced a handsome printed book of nearly 

 300 pages, with twenty full-page colored illustrations of 

 the most beautiful of the Sea Mosses, which will be found 

 of great value to the student engaged in these studies. 



No person of intelligence residing within reach of the 

 sea, should remain without a copy of this work. 



Prof. S. P. Langley has made the following calculation : 

 — A sunbeam one square centimeter in section is found in 

 the clear sky of the Alleghany Mountains to bring to the 

 earth in one minute enough heat to warm one gramme of 

 water by 1°. C. It would therefore, if concentrated upon a 

 film of water i-sooth of a millimetre thick, 1 millimetre 

 wide, and ten millimetres long, raise it 83^ in one second, 

 provided all the heat could be maintained. And since the 

 specific heat of platinum is only 0.0032, a strip of platinum 

 of the same dimensions would, on a similar supposition, be 

 warmed in one second to 26o3°C. — a temperature sufficient to 

 melt it ! 



NOTES. 



Faure batteries are now made with flat plates, the roll- 

 ing up of the sheets having been found to produce many 

 cracks in the minium. 



From exact experiments, M. Mascart finds that the 

 intensity of current capable of producing in one second the 

 electrolysis of the equivalent of a substance expressed in 

 milligrammes is equal to q6.oi webers. 



Remsen has again investigated the action of finely divided 

 iron in inducing the formation of cyanide when nitrogen is 

 passed over a hot mixture of carbon, iron, and an alkaline 

 metal ; he finds that freshly reduced iron induces a large 

 formation of cyanide, but that iron after keeping for some 

 time loses this power. 



The Physiological Effects of Mate. — Mate, or Par- 

 aguayan tea, is known to be extensively used in South 

 America, and almost universally in Brazil, the common 

 practice being to pour boiling water on some of the powder 

 (consisting of ground leaves and twigs of certain species), 

 then to suck the infusion through tubes provided with 

 strainers. MM. dArsonval and Conty have recently in- 

 quired into the action of this substance, administering it to 

 dogs, either by injecting into the veins or by introduction 

 into the stomach, and they have observed a remarkable 

 effect of it on the gases of the blood. It dimishes the car- 

 bonic acid and oxygen both of the arterial and of the venous 

 blood to a large extent, sometimes a third or even half of 

 the normal quantity. This action, which is less intense 

 during digestion, and has no necessary relation to phenom- 

 ena of excitation of the sympathetic nerve-system, is some- 

 what obscure as to its " mechanism," but its existence 

 proves directly the importance and nutritive value of the 

 aliment in question, which, consumed in such large quan- 

 tities in South America, is almost unknown in Europe. 



Prof. Ira Remsen, of the Johns Hopkins University, 

 Baltimore, has been lately experimenting as to whether the 

 chemical behavior of a metal is in any way influenced by 

 magnetic action, and has obtained some interesting results. 

 The best effects were got by placing a shallow, thin iron 

 vessel holding copper sulphate solution over the poles of a 

 magnet. Out of the magnetic field the solution would de- 

 posit a uniform coating of copper, but in the field the lines 

 marking the outlines of the poles were sharply disting- 

 uished as depressions in the deposit. In this case a per- 

 manent magnet was used capable of supporting 55 lbs. With 

 an electro-magnet still more striking effects were observed. 

 There was no deposit of copper on a narrow space marking 

 the outline of the poles. Within this the deposit was 

 fairly uniform, but outside the copper was deposited in ir- 

 regular ridges running at right angles to the lines of force, 

 and apparently coincident with the lines marking the 

 equi-potential surfaces. By increasing the power of the 

 electro-magnet, the action is intensified, and the area af- 

 fected is broadened. The cause of the phenomenon has 

 not vet been elucidated. 



Prof. E. Lommel describes in Wied. Ann. a new polar- 

 ising apparatus in which two plates of platinocyanide of 

 magnesium, cut perpendicularly to the optic axis, are used 

 as polariser and analyser, just as in the tourmaline pincette. 

 Such a section of this crystal transmits a blue light, which, 

 when the angle of incidence exceeds 2°, it is found to be 

 perfectly polarised in the plane of incidence, and it there- 

 fore can be used, if tilted to that extent out of perpendicu- 

 larity to the axis, as a polariser for a pencil of parallel blue 

 rays. One curious point in respect to the behavior of 

 thin film thus prepared is the following: Let ordinary non 

 polarised light be lcoked at through the crystal while the 

 latter is normal in the line of sight. A white central spot, 

 perfectly circular in form, and non-polarised, is observed in 

 the middle ot a blue field, which is polarised at every point 

 radially. The only other crystals which can be used for 

 polarising pincettes are the tourmaline and herapathite 

 (iodo-sulphate of quinine); the point of difference between 

 these and the platino-cyanide of magnesium is that while 

 the two former (which are negative crystals) absorb the or- 

 dinary ray, and must therefore be cut parallel to the optic 

 axis, the latter absorbs the extraordinary raj-, and must 

 therefore be cut at right angles to the optic axis. 



