M. Raspail's experiments on the granules of Pollen. 105 



object-glasses and eye-glasses, and taking care to observe with 

 the same magnifying power, the mere addition of the prism 

 renders the microscope of Amici inferior to every other micro- 

 scope, since there must be at the three surfaces of the prism a 

 triple loss of the luminous rays. But at present these two 

 kinds of microscopes are constructed with the same lenses, so 

 that my supposition is realized, and the comparative experiment 

 may be made. I request, however, those who desire to be convin- 

 ced with their own eyes, to observe with the same magnifying 

 power, and not to trust to the tricks of certain artists, who 

 exaggerate the magnifying power of a microscope in order to 

 sell it at a high price. 



With regard to the experiments in support of the fact 

 which theory establishes, they have been repeated in Eng- 

 land before M. Amici with his own microscope; they have 

 been repeated in France with an instrument made by M. 

 Amici, and recently arrived from Modena for a member of the 

 Institute ; and they have been repeated by the most skilful 

 and the oldest observers of the capital ; and it has been proved 

 that many objects — for example, the semen masculinum desic- 

 catum, — are not perceivable by the microscope of Amici. * 



These sort of revelations, perhaps indiscreet, hdve appeared 

 to me necessary, not only for the interests of science, but even 

 for those of the arts, especially since my humble labours have, 

 as I am informed, introduced the use of the microscope into 

 a number of manufactories and laboratories. They appear to 

 me necessary in reference to the interest of those young ob- 

 servers whom nature has favoured more highly than fortune, 



• In the meeting of the Academy of Sciences of the Uth August 1828, 

 M. Arago, in attempting to reply to these facts, the accuracy of which we 

 do not scruple to guarantee, has maintained that we may render these ob- 

 jects visible by the microscope of Amici by drawing out the tubes and 

 making the object approach to the object-glass, — a thing which we have 

 tried in all ways, but without success. Besides, these objects are not in- 

 visible in this microscope, on account of their smallness, but on account of 

 their transparency, and of the indistinctness of their edges. But the more 

 you draw out the tubes to magnify the diameter, the more indistinct do 

 these objects become, since you thus increase the loss of a great quantity 

 of the rays of light. The simplest experiment on this subject will serve as a 

 reply to the assertion, no doubt unpremeditated, of this learned astronomer. 



