M. Raspail's experiments on the granules of Pollen. lOS 



that they, therefore, deserve more confidence than those which 

 I have made. * This objection, which could only be urged 

 by persons little familiarized with the theory and practice of 

 the microscope, gives me the opportunity of establishing, in 

 the^r^^ place, that the superiority of microscopes cannot be a 

 guarantee of the accuracy of an observation ; and, secondly, 

 that microscopes which are vaunted as superior, are, from 

 their very construction, inferior, cceteris paribus, to all others. 



Leuwenhoek and Swammerdam used the single microscope 

 with more success than other observers did a compound one ; 

 and who will venture to pronounce himself more rich in ob- 

 servations than Swammerdam ! 



I do not know a single discovery accurately established 

 which has ever been attributed to the superiority of an instru- 

 ment, and which cannot be verified with a single lens of a line 

 focus ; and this is easily explained by considering the actual 

 state of our means of observation. 



I will not speak of solar microscopes, since, with gigantic 

 magnifying powers, these instruments give outlines too indefi- 

 nite to permit us to use them in researches which require pre- 

 cision of form and aspect 



It has been sufficiently proved that a microscope is rarely 

 susceptible of being employed with a magnifying power of from 

 800 to 1000 diameters, as the light is then weak, and the out- 

 lines indefinite. With a magnifying power, on the contrary, 

 of from 200 to 300, a good microscope shows objects with 

 clearness and distinctness. I shall suppose, however, that with 

 a power of 1000 diameters, any microscope equals in clearness 

 and distinctness the magnifying power of 200 with another 

 microscope ; the difference between the two microscopes will 

 cease to appear as marvellous, as it at first seems, when we have 

 once reduced it to its most simple expression, for in this case 

 the one will really magnify only Jive times as much as the other. 



* "We must not forget that the magnifying power itself may become a 

 new cause of illusion in reference to the automatic movements of inert bo- 

 dies. As the microscope increases the distance without augmenting the 

 duration of the motion, it is evident that a motion almost inappreciable 

 with a magnifying power of 100 diameters, will acquire the rapidity of 

 lightning with a very high magnifying power. 



