CROLL ON CLIMATE AND TIME. 719 



other to which, in turn, it serves as food. And observation shows tliat, 

 so long as there remains any organic matter which can furnish carbon, 

 the life of the moulds or of the infusoria is prolonged, but always with 

 the result of setting free, in the form of carbonic acid-gas, a part of 

 the carbon, while the life draws its other materials from the mineral 

 salts and from the nitrogen of the ammonia compounds. Tlie saline 

 substances indeed are very abundant, for at no time have they been 

 able to take on the gaseous form. And, finally, what remains ? 1. 

 Ashes, as if fire had been applied to the matter, for these slow succes- 

 sive combustions have produced the effect of fire ; 2. The last germs 

 of the last beings which lived upon the remains of their fellows. The 

 mineral substances are ready to return to the soil, the organic matter 

 has passed into the air, and when all shall have become dry the spores 

 of the moulds and the cysts of the infusoria will be borne away upon the 

 wings of the wind, to recommence, elsewhere, their work of life and of 

 destruction of life. 



The ferments, and especially the aerobic ferments or tlie beings 

 which are like them, are then the ferments of the ferments. 



After the anaerobic ferments have commenced the disorganization 

 of the material, the aerobic beings intervene and burn the organic 

 matter as completely as it would be burned by fii-e more slowly, it is 

 true, but of what importance is time in the work of destruction by the 

 life of germs ? for it is in them alone that resides the perpetuity of the 

 life of microscopic beings. 



-- 



CEOLL ON CLIMATE AND TIME.^ 



Bt E. lewis, Jr. 



THE distribution of temperatures upon the globe is a subject of 

 profound popular and scientific interest. More than any other, 

 it affects the distribution of living forms, not only in zones of climate, 

 but in s:eoloo;ical time. The contour of the earth's surface, and the 

 relations of land and water upon it, may produce important local 

 changes, or establish local faunas and floras, but these are scarcely 

 more than modifications of grander and more general results. Arctic 

 l^lants may, indeed, flourish under the equatoi*, but only on mountains 

 where an arctic climate prevails. Heat determines the limits equally 

 of the vine, the palm of the tropics, the cereals of the temperate zone, 

 and. the food of the reindeer. Whether or not tree-ferns grow in 

 Pennsylvania, and forests of pine in the Arctic Circle, depends on cli- 



' Climate and Time in their Geological Relations: a Theory of Secular Changes of 

 the Earth's Climate. By James Croll, of Her Majesty's Geological Survey of Scotland. 

 New York : D. Appleton & Co. 18Y5 



