605 



LECTURE XLIX. 



ON THE ESSENTIAL PROPERTIES OF MATTER. 



JL.UE objects, which have lately occcupied 6ur inquiries, are the most 

 sublime and magnificent tliat nature any where exhibits to us, and the con- 

 templation of them naturally excites, even in an uncultivated mind, an 

 admiration of their dignity and grandeur. But all magnitude is relativCj 

 and if we examine Avith more calm attention, 'we shall find still greater 

 scope for our investigation and curiosity, in the microscopic, than in the 

 telescopic world. Pliny has very justly observed, that nature no where 

 displays all her powers with greater activity, than in the minutest objects 

 perceptible to our senses ; and we may judge how wide a field of research the 

 corpuscular affections of matter aftbrd, from the comparatively small progress 

 that has hitherto been made in cultivating it. For while the motions of the 

 vast bodies, which roll through the heavens, have been completely subjected 

 to the most rigorous calculations, we know nothing, but from experience only, 

 of the analogies by which the minute actions of the particles of matter are 

 regulated. It is probable, however, that they all depend ultimately on the same 

 mechanical principles. We have seen, for example, that the widely extended 

 elevations and depressions of the ocean, which are raised by the attractive 

 powers of the two great luminaries, and cover at once a half of the globe," are 

 governed and combined according to the same laws, which determine the 

 motions of the smaller waves excited by different causes in a canal, the rapid 

 tremors of a medium transmitting sound, or the inconceivably diminutive 

 undulations which are capable of accounting for the phenomena of light, and 

 which must be exerted in spaces as much smaller than those of soundi as a 

 grain of sand is smaller than a mountain. Thus the annihilation of the effects 

 of the semidiurnal changes of the tide, and the preservation of the diurnal 

 change, in the harbour of Batsha, may be explained precisely in the same 

 manner as the reflection of red light from a transparent substance, of such a 



VOL. I. 4 J" 



