42 INTRODUCTION. 



possible to place a fragment of any Conferva under the micro- 

 scope, without perceiving some of the numerous forms of life 

 which dwell amongst its filaments ; and the structure of many of 

 which is so beautifully adapted to the wants of the creatures, 

 and to the existence which they are destined to lead, as to 

 raise in the mind of the beholder the liveliest feelings of 

 admiration. 



The second purpose to which the Conferva are sub- 

 servient is one of great importance, being the purification 

 of the fluid in which they dwell, laden, as it frequently is, 

 with various deleterious gases, arising from the death and 

 decomposition of various animal and vegetable substances; 

 thus deriving their own origin, for the most part, in the 

 midst of impurity, they are the agents employed in removing 

 this impurity, which salutary office they perform in the 

 following way. Amongst the most noxious of these gases to 

 animal life are carbonic acid and carburetted hydrogen ; now 

 carbon, the base of these, constitutes the pabulum, or food, of 

 plants. These two gases, then, the Conferva decompose, 

 retaining the carbon for their own support, and setting free 

 the oxygen and hydrogen ; thus not merely decomposing and 

 removing what is hurtful, but restoring to the water oxygen, 

 the essential to all animal life whether found in air or water. 

 Seeing, then, the important purpose which these apparently 

 frail and insignificant productions fulfil, who is there who 

 would venture to remove even this one small and remote link 

 from the chain of Nature's works, and would be answerable 

 for the consequences of its removal? Who can tell what 

 baneful influence might not arise, and spread disease and death 

 through whole districts? a calamity which, even as things 

 are now ordained, is occasionally permitted to overtake us. 

 Should any individual be sceptical as to the influence of 

 these productions, and whether a respiration of the kind I 

 have alluded to, and attended with the same results, really 

 occurs, let him put into a tumbler of water a little of the 

 first Conferva which he may meet with in his next ramble, 

 and, placing it in the rays of the sun, watch it for a short 



