58 
POPULAE SCIElsrCE NEWS. 
[April, 1891. 
winds being less northerly than usual is in har- 
mony with a warmer February and winter. 
D. W. 
NatiCk, March 5, 1891. 
+♦» 
[Specially Computed for Popular Science News.] 
ASTRONOMICAL PHENOMENA FOR APRIL, 
1891. 
Mercury will be in good position for observa- 
tion during the month. It is an evening star and 
comes to greatest eastern elongation on tlie morn- 
ing of April 19. It is then 20° distant from tlie 
sun, east and north, and sets about an hour and a 
half later. It may be seen as early as April 10, 
under good atmospheric conditions, and will re- 
main visible as an evening star until nearly the 
end of the month. It may be found shortly after 
sunset low down near the hoiizon, a little north 
of west. Venus is a morning star, rising about 
two hours before the sun, and is slowly approach- 
ing that body. Venus and Jupiter are in conjunc- 
tion on April 7, and at the time of nearest ap- 
proach are only 13' — less than half the diameter 
of the moon — apart. This occurs at 4 P. M., 
Eastern time, while the sun is up, and conse- 
quently cannot be seen in the United St.ates. On 
the morning of April 7, as they are seen before 
sunrise in our country, Venus is west of Jupiter 
about two-thirds of the moon's diameter, and a 
little north. On the next morning Venus will be 
to the east and north, considerably more than the 
moon's diameter away from Jupiter. Mars is still 
an evening star, setting a little more than two 
hours after the sun. It has faded out so that it is 
no longer a very conspicuous object, but may still 
be easily found if looked for. It is moving east- 
ward, aud during most of the month is in the con- 
stellation Taurus. About the middle of the month 
it is about 2° south of the Pleiades, and at the 
end of the month it is north of the ITyades — the 
V-shaped group containing Aldebaran, the bright- 
est star of the constellation. Jupiter is a morn- 
ing star, gradually increasing its distance from 
the sun. It is in the constellation Aquarius, and 
moves eastward and nortward about 6° during the 
month. At the beginning of the month it rises 
less than two hours before the sun, and at the end 
about three hours before. Saturn is on the me- 
ridian about 10 P. M. on April 1, and at about 8 
P. M. on April 30. It is in the eastern part of the 
constellation I^eo, and is moving slowly westward. 
The rings are a little wider open than they were 
during March. Uranus is in the constellation 
Virgo, and comes to opposition with the sun on 
April 19. It is then on the meridian about mid- 
night. There is no very bright star near it, but it 
lies about half-way between M. Virginis (fifth 
magnitude) and Kappa Virginis (fourth magni- 
tude). Neptune is an evening star, just north of 
the Ilyades. 
The Constellations.— The positions given are for 
the latitude of the northern part of the United 
States, and for 10 P. M. on April 1, 9 P. M. on 
April 15, and 8 P. M. on April 30. Leo Minor, a 
small constellation with no very bright stars, is 
in the zenith. Leo is just south of it, the princi- 
pal group (the Sickle) having just passed the me- 
ridian. Hydra is below Leo. Virgo is in the 
southeast, about half-way from horizon to zenith. 
Libra is just rising below Virgo. Going from the 
zenith toward the east we see first Coma Bere- 
nices and Canes Venatici ; below these, Bootes, 
then Corona Borealis. Hercules has just risen, a 
little north ot the east point. Lyra and Cygnus 
are on the horizon, just north of Hercules. Draco 
and Ursa Minor are east of the pole star. Ursa 
Major lies between the zenith and pole star, the 
pointers being very near the meridian. Cassiopeia 
is below and a little west of the pole star, and 
Perseus is west of the latter, at about the same 
altitude. Auriga is a little higher and farther 
west. Taurus is on the northwest horizon ; above 
it follow Gemini and Cancer, just west of Leo. 
Orion is setting in the west, and Canis Major in 
the southw^est. Canis Minor is above and between 
the last two. M. 
Lake Forest, III., March 4, 1891. 
Joppegponderjice. 
Brief communications upon subjects of scientific interest 
will be welcomed from any quarter. The editors do not 
necessarily indorse all views and statements presented by 
their correspondents. 
Editor of Popular Science News : 
Dear Sir: I noticed in the .lanuary number 
of the Popular Science News an item relating 
to the finding of an egg within an egg. It seemed 
less wonderful to me than something which came 
under my own observation. In preparing some 
apples for household use, a large one of the vari- 
ety known as " Northern Spy " upon being quar- 
tered disclosed a half-inch store nut with a short 
screw in it. Both nut and screw were as bright 
as if just from the manufacturer. The apple was 
perfect in all respects, and the cavity — in which 
the nut and screw exactly fitted — looked precisely 
like the other parts of the apple. The apples 
grew on a large tree in the garden near the house, 
but the limbs did not come in contact with the 
house. I should be glad to hear any teasonable 
theory on the subject. M. W. 
SOUTHPORT, Me., Feb. 20, 1891. 
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. 
Photographer.— Why is the metal magnesium 
so invariably used as a source of illumination in 
taking flash-light pictures? 
Answer. — The light, or, more properlj' speaking, 
the radiant energy from burning magnesium is 
very rich in actinic rays, wl)i(^h alone have any 
action upon the sensitive plates. These actinic 
rays are non-luminous, but accompany the light 
rays, from which they apparently only differ in 
having a shorter wave-lengtli. 
J. K. C. — What is the composition of the gum 
used on the back of postage stamps and envelopes? 
Answer. — It is composed of dextrine, a substance 
prepared by the combined action of nitric acid and 
heat upon starch. It is not poisonous, but harm- 
less in every way. It has the same chemical com- 
position as starch (Cg H,o O^), with which body it 
is said to be isomeric. 
B. M. O., Neio York. — What is the cause of the 
fading out of documents written with ink? 
Answer. — Nearly all the inks in common use 
contain organic matter as a part of the coloring 
matter. The great majority of them are princi- 
pally a combination of iron with gallic and tannic 
acids, both of which are organic acids and quite 
readily decomposed. The action of moisture, 
light, and other .agents will, after a while, decom- 
pose these salts of iron, leaving only the almost 
invisible oxide of iron to show where the « riting 
has been. The only really permanent ink is that 
prepared from some form of carbon, such as lamp- 
black, of which the Chinese or India ink is com- 
posed. Carbon resists destructive influences to a 
remarkable degree, and writings made with such 
ink will last as long as t)ie paper on which they 
are written. 
J. C. W., New York. — When were the metals 
potassium and sodium first discovered? 
Ansioer. — Humphrey Davy first prepared the 
metal potassium by electrolysis from potassie 
hydrate in the year 1807, andshorth- afterwards 
succeeded in obtaining metallic sodium, calcium, 
etc., by similar methods. Previous to this the 
metallic base of the alkalies was unknown. Me- 
tallic sodium is now produced very cheaply in 
large quantities by the Castner process, and is 
used in the manufacture of aluminium. 
LITERARY NOTES. 
An Introduction to the Study of Metallurgy, by W. 
C. Roberts-Austen, F. R. S. J. B. Lippincott 
Co., Philadelphia. 
The art of metallurgy, while a most eminently 
practical one, owes more than others to the appli- 
cation of the theoretical principles of chemistry, 
physics, and mechanics. The present work is 
notable for the judicious waj' in which theoretical 
and practical considerations are combined, and 
the clear and easily comprehended manner in 
which the beginner in the study of the art is 
introduced to the subject. There is hardly a sec- 
tion of the country iii which there are not either 
mines or metallurgical works ; and we can recom- 
mend the book to all who desire to become familiar 
with the methods of extraction and reduction of 
metals from their ores. 
Ruhher Hand Stamps and the Manipulation of India. 
Bubber, by T. O'Conor Sloane, Ph. D. 125 pages, 
27 illustnitions. Price, $1.00. Norman W. Hen- 
ley & Co., publishers, 150 Nassau street. New 
York. 
The manipulation of india rubber has hitherto 
been considered an almost impenetrable trade se- 
cret, or at the best a branch attended with much 
difficulty of manipulation. In this work the en- 
tire subject is treated exclusively from a practical 
standpoint. The details are made so clear and the 
processes are so simplified that any one of fair 
mechanical ability can undertake to make number- 
less articles of the gum. I'he fact is recognized 
that many will not feel inclined to incur heavy 
expenditure. For such, home-made apparatus, 
presses, and vulcanizers are described and illus- 
trated which will do perfectly efficient work, and 
whose cost will be almost nothing. 
Ascutney Street. A new story. Houghton, ^lif- 
flin & Co., Boston, Mass. $1.50. 
Only Mrs. Whitney could have written Ascutney 
Street, and her army of readers will find that its 
characters and incidents teach the lesson which 
the world needs to learn and practice — that real- 
ity, sincerity, usefulness, and noble aspiration 
make life not only worth living, but inflnitely 
more sane and beautiful than low aims and pre- 
tense can make it. The lesson, however, is not 
taught by preaching, but by a bright story, witli 
people and events which enlist the reader's hearty 
interest. 
Power Through Hepose, by Annie Payson Call. 
Roberts Bros., Boston. Price, .$1.00. 
This work, although showing too much the in- 
fluence of the "belsarte craze," really contains a 
great deal of practical value, nie gospel of rest 
cannot be too zealously preached, and repose of 
body and mind will often do more towards the 
cure of disease tlian medical treatment or drugs. 
The judicious perusal of this book cannot but'be 
of benefit to all. 
The Cassell Publishing Co., of N^w York, sends 
us the novel Mademoiselle Ixe, by Lanoe Falconer. 
Although in no sense a scientific work, it is an in- 
teresting and well-written story of a Russian \ihi- 
list, told with such strengih and power as to hold 
the reader spellbound. 
Pamphlets, etc., received: The Franklinic In- 
terrupted Current, by William James Morton, M. 
D., New York City ; The New Apochromatic Ob- 
jective; Deformed Diatoms, and Notes on the Cos- 
cinodiscece, by Jacob D. Cox; and from the United 
States Government Departments at Washington, 
The Hand-Book of the American Republics, Census 
Bulletins, Bulletins of the Department of Agriculture 
(Division of Entomology), Bulletin of the Coast and 
Geodetic Survey, ani\' Reports of^the Smithsonian 
Institution and the National Museum, 
