Vol. XXV. No. 8.] 
POPULAR SCIENCE NEWS. 
123 
inches. About 1 incli fell near the first of the 
month, and the rest during the cool spell, reliev- 
ing a drouth which was becoming severe. The 
average rainfall in twenty-three Junes has been 
2.72 inches, with extremes of zero in 1873, and 
5.30 in 1875. The amount of precipitation since 
January 1 has been 32.83 inches, while the aver- 
age of these six months in twenty-three years has 
been only 25.05 inches. 
PRESSURE. 
The average pressure the past month was 29.936 
hiches, witli extremes of 29.72 on the 28th, and 
30.14 on the 7th, — a range of only .42 inch. The 
mean for the last eighteen Junes has l)een 29.936 
inches, with extremes of 29.845 in 1882, and .30.056 
in 1884, — a range of .211 inch. The sum of the 
• daily variations was 2.29 inches, giving a mean 
daily movement of .076 inch. Tliis average the 
last eighteen Junes has been .115, with extremes 
of .058 and .218. The pressure the past month 
was more uniform than any June in eighteen 
years, witli a single exception. 'JTie largest daily 
movements were .20 and .16 on the 30th and 28th. 
WINDS. 
The direction of tlie wind was peculiar for 
June, as follows : 24 observations X., S., 9 E., 
25 W., 9 X. K., 10 X. W., 4 S. E., and 9 S. W., an 
excess of 30 northerly and 22 westerly, which 
gives a mean of W. 53" 45' N. The mean for the 
last twenty-two Junes has been W. 12° 27' S., 
with extremes of W. 76° 0' S. in 1876, and W. 53° 
45' N. in 1891,— a range of 129° 45', or full eleven 
and a half points of the compass. The northerly 
winds ill .June liave prevailed over the southerly 
six times in the last twenty-two years. The rela- 
tive progressive distince travelled the last month 
was 37.21 units, and during the last twenty-two 
Junes 722.0 such units, an average of 32.82, — 
showing less opposing winds than usual. 
D. W. 
Natick, July 6, 1891. 
[Specially Computed for POPULAE Science News.] 
ASTROXO.MICAT. PHEXOMENA FOR 
AUGUST, 1891. 
Mercuky is an evening star throughout the 
month, and comes to greatest eastern elongation 
(27° 25') on the evening of August 16. It is, how- 
ever, nearly 10° south of the sun, and the condi- 
tion of visil)ility is not so good as in April, but it 
can probably be seen low down in the western 
horizon soon after sunset for a few days about 
the middle of the month. It will be in conjunc- 
tion with Saturn on the evening of August 13, the 
latter being 3° 36' north of Jlercury. Venus is 
still a morning star, but is nearing superior con- 
junction with the sun, which it will reach on Sep- 
tember 18. At the beginning of the month it 
rises only about an hour before the sun, and less 
than half of that at the end. There is a very 
close conjunction with Mars at 3 A. M. on August 
22, the distance apart being only about one minute 
of arc. This will be before sunrise for places in 
the United States, and, besides, both planets are 
too near the sun to be easily seen even with a tel- 
escope. Mars passed conjunction with the sun on 
the morning of July 30, and became a morning 
star, but will remain too near the sun to be easily 
seen during the month. Jupiter is getting into 
good position for observation. It passes the me- 
ridian at 2h. 30m. A. M. at tiie beginning of the 
month, and at 12h. 20m. A. M. at the end of the 
month, and is above the horizon nearly all night. 
It is in the constellation Afiuarius, and moves 
westward about 3° during the month. The fol- 
I lowing eclipses of its satellites will l>e visible 
III. 
D. 
August 
I. 
I. 
D. 
D. 
August 
August 
II. 
D. 
August 
I. 
D. 
August 
II. 
D. 
August 
I. 
D. 
August 
I. 
D. 
August 
11. 
D. 
August 
I. 
D. 
August 
IV. 
I. 
D. 
D. 
August 
August 
11. 
D. 
August 
I. 
D. 
August 
III. 
D. 
August 
from some part of the United States. The phe- 
nomena are all disappearances, and all take place 
oft" the left-hand limb of the planet, as seen in an 
inverting telescope. Times are Eastern Standard. 
2, 4h. 55m. A. M. 
3, 5h. 5.5m. A. M. 
5, 12h. 24m. A. M. . 
5, 8h. 40m. P. M. 
12, 2h. 18m. A. M. 
12, llh. l,5ni. P. M. 
13, 8h. 47ra. P. M. 
19, 4h. 13ni. A. M. 
20, Ih. 50m. A. M. 
20, lOh. 42m. P. M. 
26, 2h. 34m. A. M. 
26, 6h. 8m. A. M. 
27, 4h. 25m. A. M. 
28, 12h. 37m. A. M. 
30, 8h. 59m. P. M. 
.Saturn is still an evening star, but is getting 
near the sun, and after the middle of the month 
will not be easily seen. At the end of the month 
it sets a little more than half an liour after the 
sun. It comes to conjunction with the sun on the 
morning of September 13. Uranus is in the con- 
stellation Virgo, and is in the southwestern slvy 
in the morning. Xeptune is in the constellation 
Taurus, and is a morning star. 
77(6 Constellations. — The positions given hold 
good for latitudes diflfering not many degrees 
from 40° north, and for 10 P. M. on August 1, 9 
P. M. on August 16, and 8 P. M. on August 31. 
Lyra is in the zenith, Aquila is coming to the me- 
ridian at about 60° altitude, and Sagittarius is low 
down on the south meridian. East of Sagittarius 
is Capricornus, at about the s.ame altitude, with 
Piscis Australis just rising below it. Aquarius 
follows Capricornus, and Pisces is just rising in 
the east. Above Pisces are Pegasus and Cj'gnus, 
the latter near the zenith. Going from the east- 
ern horizon toward the pole star, we find first 
Andromeda, and next Cassiopeia. Perseus is on 
the horizon below Cassiopeia, and Cepheus is 
above. The head of Draco is just west of the 
meridian, and a little north of the zenith. Ursa 
Elinor is mainly to the left and above the pole, 
while Ursa Major is to the left below. Hercules 
is to the west of the zenith, high up, and below it 
are Corona Uorealis and Bootes, with Virgo just 
on the west liorizon. Libra and Scorpius follow 
Virgo, and are both low down in the western sky. 
Ophiuchus is above Scorpius. M. 
Lake Forest, III., July 3, 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. 
J. C. R., Alabama. — Wliat is the cause of the St. 
Elmo's fire sometimes seen about the masts and 
rigging of vessels at sea? 
Answer. — It is caused by a discharge of atmos- 
pheric electricity through the rigging of the ves- 
sels, the pointed masts and spars furnishing ex- 
cellent conductors for that purpose. Similar 
glows of light may l)e seen about a frictional 
electrical machine, or a Rhumkoff coil when 
worked in the dark. 
R. B. C, Fenn. — I recently saw a steel drill 
which had become magnetic without having been 
in contact or near another magnet. From what 
was the magnetism derived V 
Ansioer. — The borings and chips formed by 
steel drills, and, consequently, the drills them- 
selves, are sometimes found to be magnetic. It 
is probiibly due to the inductive action of the 
magnetism of the earth, aided in some way by the 
friction. Steel bars which have remained for 
some time ju a position pointing towards the 
magnetic pole of the eartli, often become mag- 
netic from this cause, tlie earth aflecting them 
like a large magnet — as, in fact, it is. 
S. .1. F., Lousiana. — If the velocity of a river be 
doubled, will the amount of water passing a given 
point in equal times be doubled or quadrupled? 
Answer. — The amount of water flowing in a 
str(!am, other conditions remaining the same, is 
directly proportional to the velocity, so only twice 
as much water would pass down if the velocity 
was doubled. The conditions are exactly analo- 
gous to a moving railroad train. Just twice as 
many cars would pass an observer standing by the 
track in a given time if the speed of the train was 
doubled. 
C. F. T., Boston. — What is the meaning of the 
term "caustic" as used in optics? 
Answer. — A caustic is an illuminated curve, pro- 
duced by the irregular reflection of rays of light 
from a concave reflecting surface, due to splierieal 
aberration. A good illustration of caustic curves 
is found in the reflection from the interior of a 
polished silver napkin ring when placed upon a 
table cloth in a strong light. A similar curve is 
produced by reflection from the sides of a glass 
tumbler partly filled with milk, and the image is 
sometimes called by children "the cow's foot in 
the milk."' 
J. B. M., FiVf/ima.-^What is the scientific expla- 
nation of the faintly luminous disk which appears 
to be partly surrounded by the more l)rilliant and 
larger crescent of the new moon w lieu two or 
three days old? 
Answer. — The illumination of the moon's disk is 
due to the sunlight reflected to it from the earth. 
When the moon is new to us, the earth, as seen 
from the moon, would be completely illuminated 
by the sun, or " full." What we sec is really the 
surface of the moon illuminated by the " earth- 
shine "" instead of the sunshine, just as .at the time 
of the full moon the lunar inhabitants — if any ex- 
isted—might see the earth by moonlight. The 
apparent greater size of the more brilliant crescent 
is an optical illusion, due to the principle of irra- 
diation, by whioli a briglit oljject seen on a dark 
ground appears larger than it really is, while a 
(lark object on a bright ground appears smaller. 
B. M. C, Conn. — How can a perfectly homoge- 
neous light — that is, one unaccompanied by any 
other color — be obtained? 
Ansxi-er. — Very fe\\- sources of light give a pure 
and unmixed color, or, in otiier words, emit light- 
waves of a single length. Perhaps the best way 
to obtain such a light is to volatilize a salt of so- 
dium in a Bunsen gas-flame. The yellow sodium 
light is composed of rays of two diffisrent wave 
lengths only, and the difference between them is 
so extremely small that in most cases it may be 
disregarded. 
LITERARY XOTES. 
Eberhart's Elements of Entomology. A. Flanagan, 
publisher, 165 Wabash avenue, Chicago. Price, 
35 cents. 
Tins work gives full and complete directions for 
collecting, mounting, and preserving insects; a 
pictorial key to all our common insects, and a full 
explanation of technical terms. It contains forty 
full-page plates, embracing more than three hun- 
dred figures. In describing the collecting and 
mounting of insects, nothing essential is omitted. 
Useful instructions are given on time and places 
to hunt, etc. It has been adopted for use in Hed- 
ding College, Abingdon, and in the Chicago Col- 
lege of Science. Members of the Agassiz Associ- 
ation will find it particularly useful. 
P.araphlets, etc., received: On the Saurognath- 
ism of the Pici, and On the External Characters of 
Fa'tal Reindeer, by R. W. Shufeldt, M. D., Wash- 
ington; On a New Form of Corset, for Treating 
Diseases of the Spine, by Milton Josiah Roberts, 
M. D., New York; Eye Diseases of the Unborn, by 
Julian J. Chisholm, M. D., Baltimore; On the 
Mean Yearly Temperature of a Place as a Function 
of Its Latitude and Longitude, by Wilhelni Schoch, 
translated by Prof. Frank Waldo, Ann Arbor, 
Michigan ; A Modification of the Heichert Distilla- 
tion Process for Butter, by Henry Lett'mann, M. D., 
and William Beam, M. D., Philadelphia; and the 
Annual Report of the Managers of the Tale Univer- 
sity Observatory. 
