AND THE ULTIMATE POWER OF THE MICROSCOPE. 583 



primitive origination of the Entozoa, and which have not been men- 

 tioned in the memoir, I will only remark that these bodies are metho- 

 dically inoculated into every animal being in which they have hitherto 

 been discovered, which implies nothing wonderful, but only much that 

 is obscure, and which hereafter may be gradually cleared up by an in- 

 creased power of the microscope. 



2. On the perception of the smallest bright bodies I have had an op- 

 portunity of obtaining a few more results. On pressing small globules 

 of quicksilver on a glass micrometer, I easily obtained smaller globules 

 ^^ Too ^^ siyoo °^ ^ ^'"^ '° diameter. In the sunshine I could only dis- 

 cern the reflection of light and the existence of suchglobules as were y^^ 

 of a line in diameter with the naked eye; smaller ones did not affect my 

 eye either in sunshine or with a Chevalier's reverberatory lamp. I 

 however remarked, at the same time, that the actual bright part of the 

 globule did not amount to moi'e than ^^-^ of a line in diameter. Spider- 

 threads of 2o'uo"' i" diameter were still discernible from their lustre. 



3. I have lately made some experiments on the dust of diamonds, and 

 found that a diamond superficies of yJ^ of a line in diameter presents a 

 much more vivid light to the naked eyethan one of quicksilver of thesame 

 diameter. I have not yet been able to find smaller particles of diamond 

 dust possessing a good lustre. The smallest particles were from yo'q^ 

 to jo'yo of a line in diameter ; but even under the microscope no lustre 

 was to be perceived. This, perhaps, was owing to the treatment. The 

 result of these supplementary observations is, that fluid metals, since a 

 small part only of their globular superficies shines strongly, make per- 

 ceptible only very small particles of light ; that in proportion much 

 smaller lamina, especially diamond lamina, may be at least as easily 

 discerned as considerably larger metallic globules. Whether the pro- 

 portion is as 1 to 3, further investigations must teach us. Particles of 

 light having a linear form constitute the utmost limit of the power of 

 vision ; and the luminous or light-reflecting corpuscles are the fixed 

 stars of the microscopic world. 



