214 RED PARTICLES 



eye and the object, there is no reason to suppose the one can 

 deceive us more than the other. The compound having a 

 larger field, is more pleasant than the single microscope for 

 many purposes ; but the single should be always preferred by 

 those who wish to ascertain the figures of minute bodies. It 

 was this instrument, supported on a scroll, as delineated by 

 Mr. Baker (Microscope made Easy, plate 2, chap, ix), that has 

 been used in these experiments, and almost all the observa- 

 tions were made with lenses, as they are prepared by some of 

 our more skilful workmen in London. One observation only 

 was made by means of those globules made of glass, which the 

 ingenious Father de la Torre presented to the Royal Society, 

 and which they were so obliging as to lend to me. Of these glo- 

 bules, two only were fit for use when they came to my hands ; 

 viz. that which, according to Father de la Torre, magnifies the 

 diameter of the object 640 times, and that which magnifies 

 1280 times. The lenses of the greatest magnifying power 

 made in London, are those of ^ of an inch focus ; which, even 

 allowing eight inches to be the focal distance of the naked 

 eye, magnifies the diameter of the object only 400 times ; a 

 power much inferior to what may be obtained by globules, and 

 particularly by that globule which, according to Father de la 

 Torre, magnifies the diameter 1280 times ; and this globule I 

 have used in some of these experiments. But our lenses, 

 though inferior in magnifying power to these globules, are 

 much superior in distinctness. The globules are full of clouds 

 made by the smoke of the lamp used in preparing them, and 

 the object can be seen only through the transparent parts of 

 the globules, which makes it difficult to get a satisfactory view 

 of it ; this, with the trouble of adapting the object to the focus 

 of the glass, made me prefer our own lenses for all the experi- 

 ments mentioned in these sheets, except one; and it is but 

 doing justice to the ingenious gentleman above mentioned, to 

 acknowledge that the greater power of his glasses was found, 

 in that experiment, more than to compensate for their want of 

 distinctness. 



These particles of the blood, improperly called globules, are 

 in reality flat bodies ; Leeuwenhoek and others have allowed 

 that in fish, and in the amphibia, they are flat and elliptical, 

 but in the human subject and in quadrupeds almost all micro- 



