64 Mr. Fairholme on a Species of Natural Micrometer, 



Hospice du St. Bernard. 

 Latitude. Long. E. of Paris. 



Raymond. Map of the Alps 45° 52' SO 7 4° 49' 48'' 



Map of the kingdom of Sardinia, ") 



published under the direction >45 56 30 



of Government. Turin, 1819 J 

 Map attached to the new Survey 1 



of the Italian engineers. Mi- >45 48 45 4 54 



Ian, 1827 J 



Map of Savoy, byChaix, 1832... 45 52 30 4 50 



New determination 45 50 16 4 44 30 



In reducing my observations I have employed the conve- 

 nient tables of Mr. Baily, except for refraction, for which I 

 took Dr. Young's table, given in the Nautical Almanac. 

 Geneva, 3rd Nov. 1832. 



XIII. Description of a Species qf Nattiral Micrometer ; tvitk 



Observations on the Minuteness of Animalcula. In a Letter 



addressed to Sir David Brewster, by George Fairholme, 



Esq.F.G.S. 



My dear Sir, 



TN the course of a series of microscopical observations, in 



*• which I have been of late engaged, accident has thrown in 



my way a species of natural micrometer, an account of which 



I now beg leave to send you. For though it may possibly not be 



new to one so well acquainted with every thing relating to 



such subjects as yourself, yet I think it worthy of description, 



from its having brought home to my own mind the conviction 



of a fact in nature, which, though we are assured of its reality 



by numerous authors who have written on animalcula, is yet 



almost beyond the range of credibility, unless proved by actual 



demonstration. 



All authors who have treated of microscopic objects, have 

 said that there are some animalcula so inconceivably minute, 

 that it would require many thousands of them to form the 

 size of a grain of sand. Now, although we may be satisfied 

 that the extent of created objects appears quite boundless, in 

 whichever direction of the scale we may direct our thoughts, 

 yet the powers of the human understanding are so much more 

 limited, that though the tongue may express it, the mind fails 

 in its attempt to conceive defined ideas of organized beings so 

 much below the scale on which our common conceptions are 

 formed. 



I have not found, in any author, the mode by which he 

 arrived at his conclusions respecting the comparative size of 



