BRITISH ASSOCIATION. 29 



scarcely exceeding that of the corn and hay which the original pack-horse con« 

 sumed in conveying its load of 3 cwt, an equal distance. 



In thus glancing at the history of railways, we may observe how promptly the 

 inventive faculty of man supplies the device which the circumstances of the 

 moment require. ISTo sooner is a road formed fit for wheeled carriages to pass 

 along, than the cart fakes the place of the pack-saddle : no sooner is the wooden 

 railway provided than the waggon is substituted for the cart : and no sooner is an 

 iron railway formed, capable of carrying heavy loads, than the locomotive engine 

 is found ready to commence its career. As in the vegetable kingdom fit condi- 

 tions of soil and climate quickly cause the appearance of suitable plants, so in the 

 intellectual world fitness of time and circumstance promptly calls forth appro- 

 priate devices. The seeds of invention exist, as it were, in the air, ready to 

 germinate whenever suitable conditions arise, and no legislative interference is 

 needed to insure their growth in proper season. 



To persons who contend that all geological phenomena may be attributed to 

 causes identical in nature and degree with those now in operation, the formation 

 of coal must present peculiar difficulty. The rankness of vegetation which must 

 have existed in the carboniferous era, and the uniformity of climate which 

 appears to have prevailed almost from the Poles to the Equator, would seem to 

 imply a higher temperature of the earth's crust, and an atmosphere more laden 

 with humidity and carbonic acid than exist in our day. But whatever may have 

 been the geological conditions aff'ecting the origin of coal, we may regard the 

 deposits of that mineral as vast magazines of power stored up at periods immea- 

 surably distant for our use. 



The principle of conservation of force, and the relationship now established 

 between heat and motion, enable us to trace back the efi'ects which we now 

 derive from coal to equivalent agencies exercised at the periods of its formation. 

 The philosophical mind of George Stephenson, unaided by theoretical knowledge, 

 rightly saw that coal was the embodiment of power originally derived from the 

 fiun, That small pencil of solar radiation which is arrested by our planet, and 

 which constitutes less than the 2,000-millionth part of the total energy sent forth 

 from the sun, must be regarded as the power which enabled the plants of the 

 carboniferous period to wrest the carbon they required from the oxygen with 

 which it was combined, and eventually to deposit it as the solid material of coal. 

 In our day, the reunion of that carbon with oxygen restores the energy expended 

 in the former process, and thus we are enabled to utilize the power originally 

 derived from the luminous centre of our planetary system. 



But the agency of the sun in originating coal does not stop at this point. In 

 every period of geological history the waters of the ocean have been lifted by the 

 action of the sun and precipitated in rain upon the earth. This has given rise to 

 all those sedimentary actions by which mineral substances have been collected at 

 paiticular localities, and there deposited in a stratified form with a protectinff 

 cover to preserve them for future use. The phase of the earth's existence suita- 

 ble for the extensive formation of coal appears to have passed away for ever • but 



