12D 
POPULAR SCIENCE REVIEW. 
a 4 inch armour-plate. It must be observed that these shells were Hat-fronted, 
a form which has been proved to have peculiar penetrating properties. It 
may be interesting to note here that the only projectiles which have as yet 
perforated a target representing the side of the Warrior, are the 150 lb. 
cast-iron shot of the 300-pounder (unrifled) Armstrong, with a charge of 
50 lb. of powder ; and the 270 lb. solid shot of the Mersey gun, with a 
charge of 75 lb. of powder. 
MICROSCOPY. 
Spontaneous Generation. — This old theory, which some have endeavoured 
to reinstate, has been philosophically and experimentally examined by 
M. Pasteur, who has satisfactorily demonstrated, — 1st. That the air 
of inhabited places contains a greater relative number of fruitful germs 
than the air of uninhabited regions. 2nd. That the ordinary air con- 
tains only here and there, without any continuity, the condition of the 
first existence of generations sometimes considered spontaneous. Here 
there are germs, and there there are none. 3rd. There are few or 
many, according to the localities. Rain diminishes the number ; but, 
after a succession of fine days, they are more numerous. When the 
atmosphere has been for a long time quiet, germs are absent, and putre- 
faction does not take place under ordinary circumstances. From all his 
experiments, Pasteur concludes that powders suspended in the air are the 
exclusive origin, — the first and necessary condition of life in infusions, in 
putrescible bodies, and in liquids capable of undergoing fermentation. 
On the other hand, Dr. Wyman, Professor of Anatomy at Harvard 
College, U.S., has tried the same experiments as M. Pasteur, as he asserts, 
with very different results. He boiled various organic substances, — cheese, 
beef, hay, pepper, &c., and excluded the air, or purified it from germs, by 
heat and other methods of treatment, and yet, after a certain number of 
days, “ Bacteriums,” “vibrios,” and “ other living organisms ” presented 
themselves. Professor Asa Gray witnessed the opening of some of the 
flasks, and satisfied himself of the presence of infusoria in the contents. 
Mimttencss of Germs . — Some infusoria are not more than the 24,000th of 
an inch in diameter ; and if we suppose that the ova of infusoria, and the 
spores of minute fungi, are no more than one-tenth part of the linear 
dimensions of the parent organism, there must be an incalculable amount 
of germs no larger than the 240,000th or the 100,000th of an inch in 
diameter. Since, according to Sullivant and Wormley, vision with the 
most powerful microscope is limited to objects of about the 80,000th of an 
inch, we need not be surprised if infusoria and other organisms appear in 
infusions in far greater numbers than the germs in atmospheric dust, 
visible by the aid of the microscope, would lead us to expect. 
Reproduction of Infusoria. — Dr. Balbiani has published some valuable 
observations upon these minute organisms, and has satisfactorily proved 
that they are hermaphrodite, but not self-impregnating. 41 ' The reproductive 
* “ Recherches sur les Phenomenes Sexuels des Infusoires.” F. Masson 
& Fils. (A cheap and interesting pamphlet, beautifully illustrated, 
which every microscopist should read.--ED.) 
