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THE MEDITERRANEAN NATURALIST 
385 
tvo in size and an inch thick, which are ! 
laid like shingles and are practically water- 
proof, The Arabs of the East Indies make 
a durable roof paint of slacked lime, blood 
and cement. Europeans sometimes use old 
sails — made proofs against water, moukl and 
insects by paraffin and corrosive sublimate 
— for temporary roofs. 
V ARIOUS attempts have been made to 
account for the diversity in shape seen in 
eggs. A recent study convinces Ur. Nieols- 
ky that the differences may be all traced to 
gravity, and he finds his idea confirmed by 
all the eggs, in the zoological collection of 
the St. Petersburg University. He supposes 
that pressure by the sides of the ovary tends 
to elongate the egg before the shell has har- 
dened. In birds which keep a vertical posi- 
tion while at rest, as do the falcon and the 
owl, the soft egg is made short by the action 
of the weight of the bodv against the ova- 
rion pressure; while in birds that, like the, 
grebe, are nearly always swimming, the egg 
is lengthened because the bird’s weight acts 
with the compression by the ovary. The egg 
is made more pointed at one end than at the 
other in birds that like the guillemot are 
frequently changing their position — some- 
times swimming and diving, sometimes per- 
ching on the rocks, etc. 
HeYOND 29,000 feet above sea— level, the 
height reached by Glaisher in 18(32, man has 
never been able to navigate the air. Various 
problems concerning the region farther away 
— such as the temperature, the pressure, the 
quantity of moisture, the composition of the 
air, etc., — have attracted the attention of 
physicists, and have at last led to the expe- 
riments of M’ Hermite’ who during the last 
few months have been sending up pilot bal- 
loons carrying registering apparatus. These 
balloons are very light, with a capacity of 
about 100 to 200 cubic feet. Falling at dis- j 
tances from Paris ranging up to 200 miles, | 
the balloons have nearly all been returned 
♦y 
by their finders as requested on a card at- 
tached to each, and one has brought down 
records from a height of 30,000 feet. The 1 
instruments used are very light and sim- 
ple. With larger balloons and systematic 
exploration, it is hoped that the secrets of 
the air up to at least 40,000 feet may be 
made as familiar to us as those of the deep- 
est and darkest depths of the sea are gra- 
dually becoming. 
Ill R. Boys with his raclio-micrometer, says 
Knowledge, can observe a deflection of the 
instrument which is due to a temperature 
difference of less than one two-millionth of 
a degree centigrade. In one particular case 
the surface receiving the radiant heat is a 
disc only 2 millimeters (about A inch) in 
diameter, and when the scale is 30 inches 
from the mirror, the hand held about a 
yard from the instrument produces at once 
a deflection of 1G centimeters (0J inches), 
shown by the spot of light thrown by the 
mirror on the scale. Mr. Bovs also calcu- 
A' 
lates that the heat received by a halfpenny 
at 1500 feet from a candle flame would, if 
concentrated on the sensitive surface, pro- 
duce a readable deflection. 
It has been pointed out that the elaborate 
paintings of Egyptian tombs must have 
been made without lights that produced 
smoke. An American artist has suggested 
that the electric light was known and used, 
but W. Flinders Petrie finds that the dark 
rooms could have been lighted by sunlight 
reflected bv rude mirrors. 
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fHE odd fact that the forked-tail moth 
( Dicranura vinula) is a chemist of consi- 
derable capacity was shown at a recent 
meeting of the London Entomological So- 
ciety. It was previously known that its 
larvae, like ants, secrete formic acid. To 
this Mr. Oswald Latter added the new and 
surprising discovery that the mouth of the 
adult moth secretes caustic potash, with 
which it softens its cocoon and enables 
itself to emerge. Caustic potash is a pow- 
erful cautery, capable of destroying the 
human skin, and its secretion by any ani- 
mal is a unique revelation. 
