173 



instance, the large boulders of Conglomerate strewed over Llandrindod Coramon as 

 examples beyond doubt of masses of rock transported by ice, for there are no rocks of a 

 simil»r character within many miles of the place. There is one boulder lying near the 

 road below the Pump-house, which I measured. It now weighs about 100 tons, and was 

 much larger before they broke off large portions to mend the roads. 



In conversation with one of the natives a few years ago, I found that the theory 

 he entertained of this transported boulder was that the Devil in passing along had got 

 this pebble in his shoe, and as it hurt his foot, he cast it on the common. I gave the 

 old man great offence by suggesting the ice theory to him. 



Among the facts put in evidence by geologists regarding the former conditions of 

 land and sea, none are more convincing of change and system^^tic diversity than the 

 remains of plants and animals. By this testimony it appears that over every part of the 

 earth's surface, in every class of organic life, the whole series of created forms has 

 undergone great changes The prevailing opinion is that variations of the forms of 

 existing animals and plants must be exceedingly slow, since no material change has 

 taken place in our cultivated grains or amongst our domestic animals for many 

 hundreds of years of human experience. It follows, as a necessary consequence, that 

 no considerable changes, such as the total extinction of old forms of life and the intro- 

 duction of new forms, arising from such causes as are now in action, could take place 

 without allowing very long periods of time. Estimated in this way, and considering the 

 great number of living creatures that have lived through their periods and actually 

 become extinct, the antiquity of the palreozoio rocks which surround you is incon- 

 ceivable. Nevertheless, during all that inconceivable period, we have no reason to 

 suppose but that the same forces were seated in the same particles of matter ; that the 

 same influences resided on the surface of the earth ; that the same laws governed the 

 movements of the planets in their ever-changing paths around the sun. 



Geological phenomena of every order can be expressed in terms of magnitude, 

 such as the uplifting of mountains, the deposition of strata, and the numerical changes 

 of the forms of life. 



The time required to produce these effects could also be calculated it we did but 

 know the rate at which they were produced : but if we only know the limits witlan 

 which it must have operated, the result of any such attempted calculation must have 

 a corresponding uncertainty ; and, if we are positively without any knowledge of this 

 rate, all exact calculations are utterly out of the question. 



Astronomers tell us that the varying eccentricity of the earth's orbit produces cor- 

 responding changes in its temperature. By this cause the total quantity of heat 

 received by the earth within a year is increased or lessened ; and the mode in which 

 this heat is distributed on the circumpolar spaces is still more largely affected. At one 

 epoch the summer and winter temperature are made more equal : at another they are 

 made more widely different. Now, if at one of these epochs of maximum eccentricity, 

 the earth was in aphelion at the time of our winter, much heavier falls of snow might 

 take place and continue for ages, and glaciers might be largely increased both in number 

 and extent. Under contrary circumstances, less snow might fall, its duration might 

 be shorter, and its attendant glaciers might become smaller and less permanent. 

 To this latter condition the present state of the Arctic Kegions corresponds, and by 

 consulting the astronomical tables, Professor Phillips maintains that a condition of 

 extreme glaciation, dependent on the maximum ecceutricity of the earth's ■" ', 

 cannot have happened within the last 100,000 years. 



