SCIENTIFIC SUMMARY. 
437 
continuous motion of the air from a node to a loop. This might be proved 
by filling the resonant box of a tuning fork with the fumes of chloride of 
ammonium, and seeing if they are thrown out when the fork is set in vibra- 
tion. If a bell is filled with water, and a drop of oil allowed to fall on it, 
the circular film becomes quadrangular when the bell is sounded. The 
water-currents start from the nodes, and accumulate at the loops. A disk of 
glass is attached to the end of a rod vibrating longitudinally. If a glass 
drop is hung opposite the disk, it will be repelled at the centre and attracted 
around the periphery. There are then, as with air, currents outward at the 
centre, and counter-currents inward along the edges. 
Temperature of the Interior of the Earth. — From observations made on 
the well of Sperenburg, near Berlin, M. Mohr (“Les Mondes,” May 4 ) con- 
cludes that at the depth of 5,170 feet the increment of heat must be nil. 
A similar decrease of the increment of heat has been observed in the Artesian 
well of Grenelle. Hence M. Mohr draws conclusions unfavourable to the 
Plutonian theory. 
ZOOLOGY AND COMPARATIVE ANATOMY. 
Impregnation of the Boa-Constrictor . — In a recent number of the 
u American Naturalist,” Mr. S. Lockwood makes some interesting observa- 
tions on the eggs of the above animal — in fact, he puts a very important 
question to the physiologist. He says : u My friend Dr. Ivunze has shown 
me an infertile egg of a hoa which he lately obtained at the Central Park 
menagerie. The boa laid twenty-one eggs, each about the size of a hen’s 
egg. The animal made the deposit in sight of her keeper and others. She 
laid two fertile eggs, and then a sterile one, in regular succession j each third 
egg was sterile. The fertile eggs had each a young boa within. One came 
out of its shell immediately after being laid, but soon died. All the others 
died within their shells. The sterile eggs were albuminous throughout, and 
cut like cheese and smelled like sperm-oil. Could this be the balance of an 
impregnation received the year before ? 
The Cat as a Substitute for the Carrier Pigeon. — It seems that the Belgians 
have formed a society for the mental and moral improvement of cats. Their 
first effort has been to train the cat to do the work now done by carrier 
pigeons. The most astute and accomplished scientific person would have 
his ideas of locality totally confused by being tied up in a meal-bag, carried 
twenty miles from home, and let out in a strange neighbourhood in the 
middle of the night. This experiment has, however, been repeatedly tried 
upon cats of only average abilities, and the invariable result has been that 
the deported animal has re-appeared at his native kitchen-door the next 
morning, and calmly ignored the whole affair. This wonderful skill in 
travelling through unfamiliar regions, without a guide-book or a compass, 
has suggested the possibility of cats being used as special messengers. 
Recently thirty-seven cats residing in the city of Liege were taken in bags 
a long distance into the country. The animals were liberated at two o’clock 
in the afternoon. At 6*48 the same afternoon one of them reached his home- 
