Vol. XXV. No. 8.] 
POPULAR SCIENCE NEWS. 
119 
©he popcjlap Seicnce I^ew§. 
BOSTON, AUGUST 1, 1891. 
AUSTIN p. NICHOLS, S. B EDITOR 
WILLIAM J. KOLFE, LiTT.D. . . ASSOCIATE Editor 
A RECENT number of the Chemical Neies con- 
tains an interesting article by Dr. Ckookes upon 
electrical evaporation, or the efl'ect of a charge of 
electricity upon the rate of evaporation of liquids 
and solids. Two dislies containing equal weights 
of water were placed upon a delicate t)alauce, one 
being insulated and the other charged with posi- 
tive electricity from an induction coil. After an 
hour and tln-ee-quarters there was scarcely any 
difterence between the weight of tlie insulated 
water and that which had been exposed to the 
positive current. Equilibrium being restored, the 
current was reversed, the negative current being 
kept on the dish for two hours. At the end of 
this time the electrified water was decidedly 
lighter. After having again restored ecjuilibrium, 
the electrification of the dislies was I'eversed, i. e., 
the one that had before been insulated was made 
negative and the other one was insulated. In an 
hour the electrified water had become decidedly 
lighter than the insulated water. In a subsequent 
experiment in whicli the quantities were weighed, 
it was found that negatively electrified water lost 
in one and a half hom-s 1-1,000 part of its weight 
more than did insulated water. Similar experi- 
ments were undertaken upon metals, and the rate 
at which they were dissipated from an electrode 
sealed into a high vacuum tube was determined. 
Cadmium and silver were quickly dissipated from 
the negative electrode, while the metal on the pos- 
itive electrode remained practically unchanged. 
An alloy of copper and zinc, or brass, appeared 
to evaporate without separation of its constitu- 
ents ; while one of aluminium and gold was par- 
tially separated, the gold ev.aporatiug, or volatil- 
izing, under the influence of the electric current, 
"while the aluminium was left behind. Dr. Crookes 
■considers that tliis dissipation of metal electrodes 
in a high vapuum tube is strictly analogous to the 
■evaporation of water, or volatilization of metals in 
the air, the only difference being that in one case 
the electrical action which causes the molecules 
to be thrown oft" is confined to tlie surface of the 
substance experimented upon, while in evapora- 
tion or volatilization by heat the whole mass must 
be raised to the requisite temperature. 
Much has been published lately in the news- 
papers aijout a wonderful invention of Mr. VA\- 
son, by wliich views of distant objects were to be 
electrically transmitted to a distance, so that in 
combination with a telephone and phonograph a 
theatrical performance might be both seen and 
heard in a distant city. Tliis remarkable instru- 
ment, which has been baptized the " Kineto- 
graph,'" proves to be merely a modification of the 
well-known zoetrope, or wheel of life. Mr. Edi- 
son's invention simply consists of a camera by 
which pliotographs of a moving person may be 
taken in quick succession and tin-own on a screen 
from a lantern in such a manner as to reproduce 
the movements by a well-known principle of 
optics, nie kinetograph is undoubtedly an in- 
genious and wonderful invention, but it has not 
even the merit of novelty, as a similar instrument, 
invented by a Frenchman, was described in the 
Science News in May, 1800. Mr. Edison has 
suftered more than most men at the hands of un- 
scientific newspaper reporters, and it is not proba- 
ble that he ever made the absurd claims for his 
invention with which he was credited; but the 
contrast between tlie promises and performances 
of the alleged scientific wonder forcibly recalls 
that classical occurrence when " the mountain 
labored and brought forth a ridiculous mouse." 
The miignificent glacial scratches and groov- 
ings in the limestone at Kelley's Island, near 
Sandusky, Ohio, have been preserved from de- 
struction and perpetually dedicated to the public 
by the corporation owning the (juarry. These 
markings are unique of their kind, and the finest in 
the world, and their destruction would have been 
an irreparable loss to geological science. All 
geologists, and especially those who visited the 
locality with the American Association for the 
Advancement of Science, in 1888, will feel a lively 
sense of gratitude to the owners of the island for 
this generous and public spirited act. 
The scientific knowledge of Congress is well 
illustrated by its action in appropriating a large 
sum of money to carry on experiments for pro- 
ducing rain by explosions in the air at high alti- 
tudes. These experiments are now in progress, 
and balloons are filled with a mixture of hydro- 
gen and oxygen gases, and exploded in the air by 
an electric spark. As might have been expected, 
no results have as yet been obtained, except the 
wasting of the public funds to gratify the whims 
of a few scientific cranks. The idea that rain or 
any other meteorological change can be induced 
by explosions in the atmosphere is a scientific 
superstition unworthy of a moment's considera- 
tion, and with no more basis of fact than the 
influence of the moon or the sun-spots. It was, 
we believe, the same Congress which came so near 
appropriating several thousand dollars to build 
somebody's patent "flying-machine." 
The small rubber balloons sold as toys for 
children can be used to illustrate the principle of 
the diflusion of gases in a very beautiful manner. 
When sold they are filled with hydrogen gas, and 
this, by its low specific gravity, tends to dift'use 
out into the air through the thin' rubber covering 
at a faster rate than the air passes in. As a con- 
sequence, in a few hours tlie balloon is iu a semi- 
collapsed condition, and has lost its power of 
floating in the air — as many children have learned 
to their sorrow. If, now, the balloon is refilled 
with air, no diffusion will take place, and it will 
remain inflated for several da3's, the only loss 
being due to leakage. This leakage is a very dif- 
ferent matter from the mutual diffusion of hydro- 
gen and air, wliich is a true molecular movement 
through the pores of the rubber. 
An interesting experiment with Eeyden jars 
was recently shown at a scientific me(!ting in 
London by Dr. I.ouge, in which the discharge of 
one jar precipitated the overflow of another when 
the lengths of the jar circuits were properly ad- 
justed or tuned. The latter jar was entirely dis- 
connected from tlie former, and was influeuced 
merely by electro-magnetic waves emanating from 
the discharging circuit. Lengthening or shorten- 
ing either circuit prevented the overflow. The 
efl'ect could be shown over considerable distances. 
A similar observation was made by Priestley al- 
most a hundred .years ago, who noticed that when 
several jars were being charged from the same 
prime conductor, if one of them discharged, the 
others would sometimes also discharge, although 
they were not fully charged. This phenomenon 
seems to be strictly analogous to the sound vibra- 
tions induced in a string or other body of a cer- 
tain rate of vibration, by sounding a note of iden- 
tical pitch in its vicinity, and tends to confirm the 
theory that electric energy is, like sound, light, 
and heat, only a mode of motion of a wave-like or 
vibratory nature. 
» <♦► 
EuRATA.— The letter in the May issue regarding 
the presence of the ancient Phcenicians in Britain 
was written by Mr. Thomas Andrews, of Exeter, 
instead of James Andrews, as printed. The an- 
cient name of Cornwall should also have been 
printed Cornubiencis instead of Cornutiencis. 
fOriglnal In Popular Science News.] 
THE GIANT SLOTHS OF THE PAST. 
BY KATHARINE U. CLATPOLE. 
PART I. 
Passing one summer day through the Jardin 
des Plantes, in Paris, the writer was struck with 
the spectacle of a little ragged boy staring iu at 
the glass door of the Museum of Paleontology. 
Now it is not necessary to enter this museum in 
order to get a view of its contents, and our little 
urchin at the glass door was enjoying, in an inter- 
val of play, an opportunity for which many a stu- 
dent in this country would gl.adly cross the seas. 
There, before him, were skeletons of the extinct 
animals studied and described by Cuvier, the 
founder of the science of comparative anatomy ; 
some in a fossil condition, others little altered by 
the .addition of mineral matter. Many of these, 
though uni<iue specimens, would have a familiar 
look to the student. He has already made their 
acquaintance in text-books of geology, for they 
are the originals from which all illustrations of 
their species have been made. Though this is not 
the case with the gigantic creature that stands 
immediately opposite to this glass door, its bones 
have, nevertheless, been put together on the model 
of the great original. In the massive pelvis, in 
the thighs twice to three times as thick as those 
of any existing elephant, with the leg bones still 
thicker in proportion; in the small he.ad that 
seems all under jaw, and the long fore limbs with 
their formidable claws, who does not recognize 
the mighty megatherium figured in almost every 
illustration of Pleistocene life? 
In the long past a denizen of South America 
with a position well assigned in the economy of 
nature, the monster looked strangely out of place 
when, about a century ago, the first skeleton was 
brought to the light of these later days. It was 
discovered about one hundred feet below the sur- 
face in the neighborhood of Buenos Ayres, and at 
once sent to Madrid, where it shortly fell into the 
hands of Cuvier, who regarded it as the most 
astonishing and interesting discovery that had 
come under his notice. The bones clearly be- 
longed to no living species of animal, yet certala 
among them indicated their place in the system 
of quadrupeds. The sole inspection of the claws 
marked the bearer of them as an unguiculate. 
The teeth, five on each side of the upper jaw and 
four in the under jaw, — every tooth ii molar with- 
out enamel, growing from birth to death and 
never shed as are the incisors and canines of 
other animals, — gave it a right to be included 
among the edentates. There Cuvier placed it, 
though its huge and formidable frame was an 
anomaly among the little ant-bears, pangolins, 
armadillos, ant-eaters, and sloths that now form 
the family. To which of these it most nearly 
approached, Cuvier, with only the skeleton before 
him, could not determine. He therefore made a 
