140 ANNUAL OF SCIENTIFIC DISCOVERY. 



after them elephants, whose mighty remains we still find buried in the earth, 

 found a home ? Different geologists, proceeding from different premises, 

 have sought to estimate the duration of the above creative period, and vary 

 from a million to nine million years. And the time during which the earth 

 generated organic beings is again small when we compare it with the ages 

 during which the world was a ball of fused rocks. Eor the duration of its 

 cooling from 2,000 to 200 centigrade, the experiments of Bishop upon 

 basalt show that about 350 millions of years would be necessary, And with 

 regard to the time during which the first nebulous mass condensed into our 



o o 



planetary system, our most daring conjectures must cease. The history of 

 man, therefore, is but a short ripple in the ocean of time. For a much 

 longer series of years than that during which man has already occupied this 

 world, the existence of the present state of inorganic nature favorable to the 

 duration of man seems to be secured, so that for ourselves and for long gen- 

 erations after us, we have nothing to fear. But the same forces of air and 

 water, and of the volcanic interior, which produced former geological revo- 

 lutions, and buried one series of living forms after another, act still upon the 

 earth's crust. They more probably will bring about the last day of the 

 human race than those distant cosmical alterations of which we have spoken, 

 and perhaps force us to make way for neAV and more complete living forms, 

 as the lizards and the mammoth have given place to us and our fellow- 

 creatures which now exist. 



Thus the thread which was spun in darkness by those who sought a per- 

 petual motion has conducted us to a universal law of nature, which radiates 

 light into the distant nights of the beginning and of the end of the history of 

 the universe. To our own race it permits a long but not an endless exist- 

 ence; it threatens it with a day of judgment, the dawn of which is still hap- 

 pily obscured. As each of us singly must endure the thought of his death, 

 the race must endure the same. But above the forms of life gone by, the 

 human race has higher moral problems before it, the bearer of which it is, 

 and in the completion of which it fulfils its destiny. 



IMPOSSIBLE PROBLEMS. 



The following paper on " impossible problems," published during the past 

 year by the well known mathematician, De Morgan, presents some points 

 of novelty and scientific interest : 



When we find a long and enduring discussion about any points of 

 speculation, we naturally ask whether there be not some verbal difficulty at 

 the bottom. What is the solution of a problem? It is the showing how to 

 arrive at a desired result, under prescribed conditions to the means which are 

 to be used, and as to the form in which the result is to be presented. There 

 are then three possibilities of impossibility. The desired result may be 

 among non-existing things ; the prescribed conditions may be insufficient ; 

 the form demanded may be necessarily unattainable. And any one of these 

 things being really the case, it may be impossible to demonstrate that it is the 

 case. Human nature, which always assumes that it can know whatever can 



