9 6 



SCIENCE. 



PHYSICAL NOTES. 



Copper-Plating on Zinc. — The use of Cyanide baths 

 for plating on zinc has the double disadvantage of 

 being poisonous and expensive. Hess, it is stated, has 

 overcome the objections by rendering the cyanide bath 

 unnecessary. This he accomplishes by the use of an 

 organic salt of copper, for instance, a tartrate. Dissolve 

 126 grammes sulphate of copper (blue vitriol) in 2 liters 

 ot water; also 227 grammes tartrate of potash and 2S6 

 grammes crystallized carbonate of soda in two liters 

 of water. On mixing the two solutions a light bluish- 

 green precipitate of tartrate of copper is formed. It is 

 thrown on a linen filter, and afterwards dissolved in half 

 a liter of caustic soda solution of 16° B., when it is ready 

 for use. The coating obtained from this solution is very 

 pliable, smooth, and coherent, with a fine surface, and ac- 

 quires any desired thickness if left long enough in the 

 bath. Other metals can also be employed for plating in 

 the form of tartrates. Instead of tartrates, phosphates, ox- 

 alates, citrates, acetates and borates of metals can be used, 

 so that it seems possible to entirely dispense with the use 

 of cyanide baths. 



MM. Lethuiller and Pinel, of Rouen, have devised an 

 electrical indicator, by means of which the water-level in 

 steam boilers may be ascertained at any distance. The 

 arrangement employed for this purpose consists of an in- 

 dicating tablet, which may be placed in any part of the 

 establishment, however remote from the boiler-house, in 

 the office of the engineer or the superintendent, 01 within 

 reach of the boiler inspector. This tablet is connected 

 with the electric indicator, which is fixed at the top of a 

 vertical tube above the boiler, by two electric conducting 

 wires. At the lower part of the scale of the indicator are 

 placed two pieces of copper, upon each of which is fastened 

 a small plate. These platinum wires are superposed at a 

 distance of 0.08 in. When the index, which is attached to 

 a vertical rod connected with the float in the boiler, de- 

 scends, it rest on the upper plate of platinum, depresses it, 

 and puts it in contact with the lower plate. An electric 

 current is thereby established from a battery connected 

 with the apparatus, causing a bell on the indicator to ring, 

 while at the same time the si^n "low water" appears on the 

 tablet. Similar pieces of copper and platinum are fixed at 

 the upper part of the scale, and when the index reaches this 

 limit, in consequence of the rising of the float, the bell rings 

 as before, and the indication "high water" is shown on the 

 tablet. In order to remove the warning word from the tab- 

 let, a button is pressed, which returns the indicating parts 

 to their normal position. 



It is but a short time ago we were pleased to see an 

 original article, written by a Japanese, on the combustion 

 of carbon, at low temperatures, and again we are remind- 

 ed of the " new departure" in an article on the determina- 

 tion of the acceleration due to the force of gravity, at Tokio, 

 Japan {Amcr. your, of Set. for Aug.), in which the writer, 

 Mr. T. C. Mendenhall, acknowledges the assistance of 

 Messrs. Tenaka and Tenakadate, of the Department of 

 Physics, of the Imperial University of Japan. The method 

 employed was the usual one, which involves the use of a 

 good chronograph and a break-circuit clock, together with 

 an arrangement by means of which the experimental pendu- 

 lum can be made to record its own beats upon the chrono- 

 graph at any time. As the resistance offered to the pendu- 

 lum, although small, is perceptible, it will interfere with 

 its motion if the pendulum is obliged to operate the break 

 circuit at each beat. Mr. Mendenhall obviates the difficul- 

 ty by making the pendulum break the circuit but twice, 

 once at the beginning of the period and once at the end. 

 By this process the experiment need not be protracted, and 

 yet a great degree of accuracy may be obtained. As the 

 average duration of the experiment is only twenty minutes, 

 differences of temperature may be neglected, and all the 

 conditions may be maintained constant during the whole 

 time of the swing. 



Prof. Joseph Le Conte, in an article read before the 

 National Academy of Science, takes issue with Helmholz 

 on some important points in the latter's conception of the 

 Law of Listing. This law has important bearing on the 

 phenomena of binocular vision. Its application, however, 

 from the conclusive experiments of Prof. Le Conte, must 

 be limited to other motions of the eye than those taking 

 place in strong convergence. In thus differing from the 

 high authority of the great German, Prof. Le Conte in a 

 philosophical spirit worthy ot more general imitation, 

 deprecates the too common method of trying to verify the 

 results of others, rather than to determine the law for one's 

 self. 



As a considerable difference exists between the results 

 obtained by the formula; of Le Verrier and Stockwell in 

 calculating the longitude of the perihelion and the eccen- 

 tricity of the earth's orbit, Mr. R. W. McFarland in August 

 Journal of Science, gives a comparative table, in periods of 

 10,000, extending over 4,500,000 years. It is accompanied 

 by a chart (with ordinates at intervals of 50,000) dividing 

 the time into two periods, viz., for 3,250,000 years before, 

 and 1,260,000 years after A. D., 1850. An inspection of the 

 table shows that the motion of the perihelion is exceedingly 

 irregular and occasionally retrograde. 



Jas. Croll, F. R. S., makes mention of an article written 

 by himself in Phil. Mag. xxxiii., 1867, pp. 213-216, which 

 may not have been before presented to the American public, 

 in which he accounts for the remarkable fact, first observed 

 we believe, by Mr. Glaisher, that the difference of reading 

 between a black-bulb thermometer exposed to the direct 

 rays of the sun, and one shaded, diminishes as we ascend 

 into the atmosphere. Mr. Croll deduces from this, that 

 radiation into stellar space is the medium for the preserva- 

 tion of snow in elevated places, and the protective action of 

 aqueous vapor the cause of its melting in places where there 

 is a greater snow-fall, a remark in perfect harmony with 

 Prof. Tyndall's important discovery regarding the influence 

 of aqueous vapor on radiant heat. 



Professor Henry Draper read a paper of great interest 

 before the Royal Astronomical Society in Mav, which now 

 appear for the first time in this country. — {American Jour- 

 nal of Science.) He gives facts which seem to point to the 

 conclusion that it is not improbable that Jupiter is still hot 

 enough to give out light, though perhaps only in a periodic 

 or eruptive manner. He applied spectroscopy to the problem 

 and submitted to the Astronomical Society the photograph 

 upon which he based his ingenious speculations. We are 

 glad to see that Prof. Draper has been assisted by his wife 

 in these observations. Humboldt long ago suggested as an 

 advantage to science that the finer senses of women be used 

 in astronomical research. 



A new and abundant locality for the mineral Danburite 

 has been discovered by Mr. C. D. Nims, the mineral col- 

 lector, in St. Lawrence County, N. Y., which is said by 

 Messrs. Brush and Dana {August American Journal of 

 Science), to be of considerable extent and importance. The 

 mineral occurs massive, micro-crystalline and also in 

 druses of magnificent appearance, where, in one instance, a 

 crystal was found 4 inches long and 2)4. inches macro-diago- 

 nal width. The crystals were originally embedded in a 

 younger calcite which has been much eroded. The para- 

 genesis (in a matrix of granitic rock) seems to be, from their 

 description, quarz, danburite, pyroxene and tourmaline and 

 last a pink calcite. It is also accompanied by pyrite. 

 Messrs. Brush and Dana elaborate their description and en- 

 rich it with many angular measurements. The homoeomor- 

 phism of topaz, and danburite are conclusively demon- 

 strated, and an Opportunity has been seized to supplement 

 and revise the observation made at the time Smith and Brush 

 worked on the original mineral from Danbury. 



O. A. M. 



