278 SCIENTIFIC ILLUSTRATIONS [Pop 



And in both cases we find that reflection enables us to account 

 for a great deal of phenomena which at first appeared inexpli- 

 cable. The lower stratum of intelligence, like the lower clouds, 

 always moves slowly, and for the same reason. Any person 

 looking from a mountain, on a cloudy storm raging in a valley 

 below, may observe that the lower part of the storm moves with 

 less velocity than the upper part, producing an irregular rolling 

 or tumbling motion of the clouds, that evidently arises from 

 the resistance which that part of the wind encounters that 

 presses on the surface of the earth. The frictions and obstruc- 

 tions on each particular part of the surface impede the progress 

 of the lowest part of the air, and that other portion, which 

 immediately follows, climbs over the lowest stratum of air, but 

 in so doing it is itself impeded by the obstacle it has to encounter 

 in the lower and retarded air. A third portion of air then 

 climbs over the second, and in so doing is itself retarded, and 

 in this way successive strata of air follow and climb over the 

 other strata that present obstacles to their progress, and thus 

 form overlapping and rising current, moving with increasing 

 velocities as they proceed at a greater distance from the obstruc- 

 tions on the surface of the earth. ON. 



Growth and Persistency of Popular Ideas. 



The way in which popular ideas have been introduced into 

 English society, have taken root and persistently flourish, re- 

 minds us of the account Mr. M. G. Lewis, M.P., gives 

 of the introduction of vassals grass into Jamaica. It appears 

 that many years ago a new species of grass in a small quantity 

 was introduced into the island for the purpose of feeding 

 pigs. Its seeds soon became scattered about by the birds, 

 and it then took possession of the cane-pieces, whence to eradi- 

 cate it was often, and is, an utter impossibility, the roots being 

 as strong as ginger and insinuating themselves (like Liberal 

 ideas) underground to a great extent. In a very short time it 

 overran several parishes, obtained a footing in the island, and 

 increased the cost of cultivation of the cane by at least, one-third. 

 Where the moral and intellectual soil of a country is favourable 

 to the growth of particular ideas, and these are distributed by 



