Infusory AiwinaU not formed from Dead Matter. 821 



latory motions, this number gives a tangible limit for their 

 maximum, although somewhat arbitrary, and therefore one ex- 

 pression for their degree of minuteness. If wp were to conclude 

 the minuteness of these elementary particles from tlie .want of 

 weight of highly condensed light, or masses of ether^ the limits 

 of these maxima must be considerably extended. All these, 

 however, are mere hypothetical magnitudes when we come to 

 express them in numbers. 



The coloured phenomena between glasses which are nearly in 

 contact, permit likewise of some inferences regarding the mag- 

 nitudes of the so-called elements of colour. Newton has already 

 fixed at -i^-^-^js-^' <i the smallest interval, which gives a white co- 

 lour, which is a little more than uJ^u") ^^^^ Haiiy has calcu- 

 lated, from the different refractive powers of mica, that a plate 

 of this substance, which produces the same effect as the above 

 layer of air, must be 550^0(5 of a mihimeter, or goc^oo" *" 

 thickness. 



With respect to solid inorganic as well as organic bodies, 

 Robert Brown's microscopic measurements of the years 1827 

 and 1829, fixed the size of the smallest observable particles 

 which he saw in active movement, and of a globular form, at 

 about ^^\^^' to jffigo^ or from ^^^J" to ^y^^/' in diameter. 



J. F. W. Herschel, in his Optics (1829), says, that he has 

 seen bodies, through an Amician microscope, magnifying 3000 

 times, but that he was far from supposing that he had at all 

 succeeded in resolving bodies into their constituent atoms. 



Infusory Animals not formed directly from dead matter. — 

 M. Dumas, the chemist, from his own observations, main- 

 tained, in 1825, that the elementary globules of dead orga- 

 nic matter might be seen and counted by the aid of a good 

 microscope ; that they formed other larger bodies by the simple 

 union and augmentation of their masses, which were at first in- 

 fusory animalcules, capable of being resolved by the electric 

 shock into their primitive elements, when they assumed the 

 form of a raspberry. — {Diet. Class. d'Hist. Natur. Article Ge- 

 neration, p. 195.) In the same place, p. 81, the author be- 

 lieves that, in the present state of chemistry, it was possible to 



VOL. XIII. NO. XXVI. OCTOBER 1832. X 



