Early History of the Microscope. 3 



quamvis minutje et obscur®, per vitream pilam aqua plenam, 

 majores clarioresque cernuntur." " Letters, though small and 

 indistinct, are seen larger and clearer through a glass bubble filled 

 with water," which, I think, proves that the Romans, at any 

 rate, used a magnifying-glass as such. 



Now to come down to the period when the microscope began 

 to assume a shape worthy the name we find the instrument to 

 have been what is known as a single microscope, i. e., consisting 

 of a single deep convex lens set in metal, having a very small 

 aperture. As early as 1656, however, we find inventive genius 

 at work in the person of a Dr. Hooke, who, in the preface to his 

 ' Micrographia lUustrata,' describes the manner of making tiny 

 glass globules, and about the year 1665 these globules began to 

 be occasionally applied to the single microscope. Of course the 

 magnifying power of such a lens is very great, but unless 

 Dr. Hooke was satisfied with a very small field, the spherical 

 aberration which would occur must of necessity have made his 

 observations somewhat distorted. Here again we find an inven- 

 tion attributed to two people, some afiSrming the inventor to have 

 been a Monsieur Hartsoeker ; but, as the first recorded discovery 

 of this observer is that of Spermatozoa, made when he was 

 18 years old, in the year 1674, he must have begun inventing very 

 young to have been previous to Dr. Hooke's description in 1656. 



To give you an example of the patience with which these 

 early observers worked, I take bodily a description of the mode 

 of manufacturing these globules, as given by Dr. Hooke in bis 

 'Letters and Collections,' 1678. He says : — "Take a small rod 

 of the clearest and cleanest glass you can procure, free, if 

 possible, from blebs, veins, or sandy particles ; then, by melting 

 it in a lamp made with spirit of wine or the purest and clearest 

 salad oil, draw it out into exceeding fine and small threads ; take 

 a small piece of these threads and melt the end thereof in the 

 same flame, till you perceive it run into a small drop or globule 

 of the desired size ; let this globule cool, then fix it upon a thin 

 plate of brass or silver, so that the middle of it may be directly 

 over the centre of a very small hole made in this plate, handling 

 it till it is fixed by the before-mentioned thread of glass. When 

 the plate is properly fixed to your microscope and the object ad- 

 justed to the focal distance of the globule, you will perceive the 

 object distinctly and immensely magnified. By this means," 

 says Dr. Hooke, " I have been able to distinguish the particles 

 of bodies, not only a million of times smaller than a visible point, 

 but even to make those visible whereof a million of millions 

 would hardly make up the bulk of the smallest visible grain of 

 sand ; so prodigiously do these exceeding small globules enlarge 

 our prospect into the more hidden recesses of nature." 



Now, gentlemen, I should be sorry to argue with a man so 



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