INTRODUCTION. 43 



time ; he will soon observe globules of a gas, at first small, 

 but soon becoming larger, to collect upon the surface of the 

 filaments, which, when they have attained a sufficient size, 

 will quit their attachment, rise to the surface of the water, 

 and at last lose themselves in the surrounding air. This 

 will, I think, satisfy him that a respiration of some kind is 

 carried on ; and should he wish to ascertain the nature of the 

 gas thus eliminated, whether it be really oxygen or not, this 

 may be done by procuring a considerable quantity of any 

 floating species of Conferva, and placing it in a trough of 

 water, over which should be put a glass jar also filled with 

 water, having an air-tight collar adapted to it, so disposed as 

 to catch the gaseous globules as they ascend. As soon as 

 the glass jar becomes filled with the gas, let the air-tight 

 collar be removed and a piece of ignited phosphorus be 

 quickly plunged into the interior of the jar, when the brilliant 

 and dazzling combustion which will instantaneously ensue 

 will afford a proof conclusive of the nature of the elimination. 

 The honour of this discovery, if it can be deemed one, for it 

 is but the extended application of the common principle of 

 the respiration of plants generally, is in this country attri- 

 buted to Priestley ; but so obvious is it that it scarcely re- 

 quired the penetration of a mind like his for its detection : 

 Vaucher alludes to it cursorily. 



The third use of the Conferva is a moral one. Every 

 created thing, rightly viewed, is capable of imparting this 

 moral lesson, be it the kingly lion or the spurned reptile; 

 the beautiful and scented flower, or the more humble pro- 

 ductions which have been engaging our attention. There is 

 no imperfection acknowledged in nature, nor are there, 

 strictly, degrees of comparison; everything is superlative, 

 is best and perfect from the hands of God who made it, alike 

 unsurpassable and inimitable. 



Then, lastly, there is the intellectual benefit derived by those 

 who study this or any branch of Nature's works. There are 

 those who regard the pursuits of natural history as trivial and 

 tending to no useful purpose ; but these are but superficial ob- 



