t>6 
SCIENCE. 
PHYSICAL NOTES. 
Copper-Plating on Zinc. — The use of Cyanide baths 
for plating on zinc lias 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 286 
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 0 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 tartiates, 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. Lethuileer 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, or 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 sign “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 (Amer. Jour, of Sci. 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 Ilelmholz 
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 of 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 formulae 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. Croix, 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 Jotirnal 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 y 2 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. 
