164 
POPULAR SCIENCE NEWS. 
[November, 1S90. 
water would run till the river was frozen over, and 
thus protected the water from the intense cold. 
I write this because I saw in your paper a question 
as to how anchor ice is formed, and no explanation 
given. I have never seen the true explanation in 
books, but it must be in some of the modern chem- 
istries, as I once examined a class of joung ladies, 
and they had the right explanation. 
Brooklyn, N. Y. 
<♦> 
GLACIERS: THEIR FORMATION AND 
THEIR MARCH. 
In high valleys, among the mountains whose tops 
are covered with perpetual snow, are often found 
seas of ice, called "glaciers." They are formed 
thus: Snow that falls upon lofty mountains melts 
very little even in summer. So in valleys high up 
among the mountains it gathers to a great depth, 
and, from the weight of the snow lying above, the 
lower layers become icy, as a snowball does when 
squeezed. The upper crust melts a little during the 
heat of the day, and the water sinks down through 
the snow, and then freezes at night. From this 
melting and freezing the mass of snow is soon 
changed into a sea of ice. 
In travelling down valleys those ancient glaciers 
left traces of their journey. Over all the places 
where the ice-seas passed, the rocks are rounded 
and highly polished. A field of these rounded 
rocks, when seen from a distance, looks like a field 
filled with sheep crouching on the ground, and 
Swiss geologists have called them roches moutonnees 
— " slieep-like rocks." In a valley along the summit 
of thi; Rocky Mountains, near the "Mountain of 
the H 3ly Cross," there is a beautiful display of these 
polisl-ed, rounded rocks. 
As the glaciers moved down the valleys, great 
rockS: frozen fast in the ice on the sides and at 
the bottom, scratched and marked other rocks as 
they ))assed by and over them. Sometimes these 
scorirgs are very broad and deep, for the immense 
rocks :he glaciers carried were like strong, powerful 
tools n the grasp of a mighty engine ; sometimes 
the li les are as fine as those of a fine engraving. 
They isually run all one way, and, by looking at the 
direct. on in which the lines run, one can tell the 
direction in which the glacier moved. In the sand- 
stone west of New Haven, Connecticut, the deep, 
broad scorings can be plainly seen, running toward 
the southeast. The height at which these scratches 
occur tells us something of the depth of the ice. 
Markings in the White Mountains indicate that the 
ice was more than a mile deep over the region now 
known as northern New England. 
Wherever the glaciers melted, they left an im- 
mense amount of "drift," that is, sand, gravel, and 
stones of all sorts, which had been frozen in the ice 
when the glaciers were forming. The stones of this 
drift are of all sizes. Some are as small as pebbles, 
others as large as small houses. There is one at 
Bradford, Massachusetts, which measures thirty feet 
each way, and weighs four and a half million 
pounds. There is another on a ledge in Vermont 
which is even larger than that, and which must 
have been carried by the ice across a valley lying 
five hundred feet below where the stone now is, 
showing that the ice was five hundred feet thick. 
Great boulders of trap rock extend throngh Con- 
necticut on a line running to Long Island Sound ; 
and, as some of the same kind are found in Long 
Island, the glacier is believed to have crossed the 
Sound, carrying these rocks with it. An immense 
statue of Peter the Great, in St. Petersburg, stands 
on one of these glacier boulders of solid granite, 
which weighs three million pounds. One of the 
largest boulders in America is in the Indian village 
of Mohegan, near Montville, Connecticut. The 
Indians call the rock "Shehegan." Its top, which 
is flat and as large as the floor of a good- sized room, 
is reached by a ladder. 
Sometimes these boulders are found perched upon 
bare ledges of rock, so nicely balanced that, though 
of great weight, they may be rocked by the hand. 
They are called " rocking-stones." Near the little 
Connecticut village of Noank, on Long Island 
Sound, there is an immense boulder called by the 
people there "Jemimy's Pulpit." It was formerly a 
rocking-stone, but the rock has worn away below it 
and it can no longer be moved- — Teresa C. Crof- 
TON, in St. Nicholas. 
SCIENTIFIC BREVITIES. 
Lake Champlain. — The greatest depth of Lake 
Ghamplain is 402 feet, and consequently parts of the 
bottom of this lake descend 300 feet below the level 
of the Atlantic Ocean. The lake is highest in May, 
when it is 2.18 feet above the mean, and lowest in 
September, when it is 0.96 feet below it; it is above 
the mean also in the months of March, April, and 
June. 
The Alterations in the Conductivity of pure 
copper, aluminium, and magnesium, and of com- 
mercial zinc and German silver, after a lengthened 
exposure to a high temperature, have recently been 
investigated by J. Bergmann. Discs, seventy milli- 
metres in diameter, were heated to 300° C, and 
maintained at that temperature for one hour, and 
then allowed to cool slowly. The conductivity 
of copper was increased by something like 2.4 per 
cent, by this process; that of aluminium, magne- 
sium, and zinc being increased, respectively, 5, 6.8, 
and 2.4 per cent. The conductivity of the alloy 
was, on the other hand, diminished by about 2 per 
cent. 
The Motions upon the Surface of Water 
of small particles of camphor, are supposed to be 
due to the diminished surface tension of water 
impregnated with that body. In order that the 
motions may be lively, the utmost cleanliness is 
imperative, and the most minute quantity of oil is 
known to be sufficient to impede these gyrations. 
In view of the great interest which attaches to the 
determination of molecular magnitudes. Lord Ray- 
leigh has thought it worth while to measure the 
quantity of oil necessary to counteract the move- 
ments of the camphor. Every care was taken to 
measure the oil accurately, and to exclude the possi- 
bility of any grease but such as was applied reaching 
the water. It was found that the minute quantity 
of o 81 milligram of oil was sufficient to stop the 
movements, the surface over which this volume was 
spread being 84^ square centimetres, so that the 
thickness of the oil film, calculated as if its density 
was the same as in the more normal state of aggre- 
gation, was 1.63 micro-millimetres. 
Mexican Onyx. — Mexican onyx, says the Jewel- 
ers' Weekly, is a form of stalagmite, and its colors 
are formed by oxides of metals in the earth over the 
caves through which calcareous water passes. Gold 
is represented by purple, silver by yellow, iron by 
red, copper by green, and arsenic and zinc by 
white. Volcanic eruptions and earthquakes have 
almost destroyed the caves in which onyx exists, 
and the native Indians who mine it have to cut 
through masses of ruins. Blocks of the material 
are quarried in a primitive way, in order not to 
shatter the substance. Deep round holes are drilled 
by hand on a line. In each hole is inserted a 
snugly fitting piece of wood, which has been 
grooved from end to end. Hot. water is poured into 
the grooves at night. This swells the wood and the 
block is split along the line without damage. The 
natives then saw the blocks into slabs and polish 
the surface by hand. Each piece is semi-transpar- 
ent, and, when placed between the eye and a strong 
light, presents a remarkably beautiful efliect in form 
and color. 
— <♦< 
QUESTIONS AND ANSWERS. 
Letters of inquiry should enclose a two-cent 
stamp, as well as the name and address of the 
writer, which will not be published. 
Questions regarding the treatment of diseases 
cannot be answered in this column. 
E. T. A., Mass. — The German play of William 
Tell speaks of a rainbow in the night. Does such 
a phenomenon ever occur? 
Answer. — Lunar rainbows are occasionally ob- 
served under favorable conditions, but they are very 
uncommon. The reference in the play is probably 
to the lunar halos, or circles surrounding the 
moon, which are familiar to everyone. They indi- 
cate the presence of moisture in the upper air, and 
usually justify their reputation as prophets of rainy 
weather. 
L. P. H., Plymouth. — Does the top of a wheel 
move faster than the bottom } 
Answer. — The top of a carriage wheel moves 
faster, with reference to the observer, than the bot- 
tom, because, in addition to its movement of rota- 
tion, it has the direct forward movement of the 
carriage as a whole. The bottom of the wheel 
moves in an opposite direction to that of the wheel 
itself, and, as the two motions partially neutralize 
each other, the bottom part appears to move past 
the observer more slowly than the top. Instanta- 
neous photographs of moving carriages often show 
this very clearly, the top of the wheel being blurred, 
while the lower part is quite distinct. Of course, in 
the case of a fixed wheel, — a pulley on a shaft, for 
instance, — all parts would move with the same 
velocity. 
F. M. W., Indiana. — Vulcanized rubber will, after 
a while, undergo a sort of spontaneous decomposi- 
tion, becoming hard and brittle. It is said that 
soaking in dilute ammonia will restore its softness, 
but we doubt if there is any really effective way to 
do it. The best way is to buy only freshly-made 
rubber tubing, etc., and use it as much as possible 
during its " life." 
R. M. S., New Jersey. — What can I use to prevent 
grass and weeds growing in gravel walks and drive- 
ways .' 
Answer. — A liberal mi.xture of common salt with 
the gravel is about as effective as anything, but 
if there are grass borders or flower-beds near by, 
care should be taken that the rains do not wash the 
salt upon them from the path. 
M. B. E., Detroit.. — Tne specific gravity of the 
solid metals is only approximately proportional to 
their atomic weights. Lithium, the lightest solid 
metal known, (sp. gr. .058), has the low atomic 
weight of 7. Uranium has the highest atomic 
weight of any known element, 240, and a specific 
gravity of 18.4; while osmium, with the much 
higher specific gravity of 22.48, has an atomic 
weight of only 195. Mercury, with an atomic 
weight of 200, has a specific gravity of 144. In 
the gaseous condition, however, the atomic and 
molecular weights of all substances bear a very 
simple and exact relation to their specific gravities, 
this principle being one of the corner stones of 
modern chemical philosophy. 
J. D. C, Boston — Tellurium is an element closely 
related chemically to selenium and sulphur. It is a 
very rare element, but has recently been found in 
Colorado in masses of considerable size, some 
weighing as much as twenty-five pounds. No prac- 
tical use has ever been made of it. 
N. B. P., Albany. — Is the universe believed to be 
of indefinite extent, or is there a limit to the myri- 
ads of stars which we look out upon from the earth .' 
Answer. — It can be proved that, unless light is 
extinguished in passing through space, there must 
be a limit to the universe, or the entire sky would be 
a blaze of light. We must, therefore, believe either 
that our universe contains only a certain number 
of self-luminous bodies, or else that, in some wa3', 
light is absolutely ^extinguished in passing to us 
through the cekstial spaces. Either theory is 
plausible enough, but the question still remain's an 
open one. 
