286 THE NATURAL HISTORY OF 



colour, green, yellow, &c, are of this description. The 

 larger kinds are chiefly of the insect or vermes tribes, and 

 of which one, denominated the monoculus pulex, is some- 

 times so abundant as to change the water apparently to a 

 deep red. A similar appearance is likewise caused by the 

 cercaria mutdblis, when it varies from a green to a red 

 colour; the vorticella fasciculata also changes it to a green, 

 and the rotatoria to yellow. To this section also must be re- 

 ferred many of the acaca and hydrachna genera. 



The microscope discovers numberless myriads of these 

 diminutive creatures to our view in most fluids, among which 

 I may mention sea-water, the colour of which I have reason 

 to believe is given by the animalculae ; fresh river or rain 

 water, the animal fluids, vinegar, beer, dew, &c. Also in 

 animal or vegetable infusions, and many of the chalybeate 

 waters. 



Those who have made the most minute researches, and 

 accurate enquiries into the natures of the several objects sub- 

 jected to their senses, have found that the substances upon 

 which they employed their curiosity were often quite dif- 

 ferent to what at first they appeared to be. Thus, for in- 

 stance, the whole earth has been replenished with an inex- 

 haustible store of the least of which we should the least 

 suspect ; that is, an infinite number of animalcule floating 

 in the air we breathe, sporting in the fluids we drink, or 

 adhering to the several objects which we see and handle. 

 The conjectures and theories relating to the production, 

 generation, structure, and uses of these animals, have been 

 as various as were ever contrived by caprice, or embraced 

 by credulity. Not to bewilder the reader, however, in these 

 labyrinths, but to prove the truth of this assertion of these 

 animals' existence, we have recourse to the microscope, by 

 which we are not only able to distinctly see them, but in 

 some degree to distinguish their shapes and peculiarities of 

 motion, particularly by Lieutenant Drummond's and Hol- 

 land's Oxy-Hydrogen Microscopes, Carpenter's Solar 



