and Laboratory Methods. 1621 



NOTES ON THE MICROSCOPE. 



I. Early Microscopes. 



These notes are offered with no pretense to completeness or originaHty. If 

 they give usable information regarding the origin, development, construction, 

 use, and care of the microscope to any who do not have it, they will have fulfilled 

 the purpose for which they were intended. 



Lenses have been known from very early times, lens-shaped pieces of rock 

 crystal having been made as early as 720 B. C. Although simple 

 magnifying lenses were used as such in 1276 by Roger Bacon, a monk, 

 it was not until about 1590 that the first combination of lenses into what 

 might be termed a crude microscope was made by Hans and Zacharias 

 Janssen in Holland, and even this is in some doubt. The instrument 

 attributed to them consisted of two tubes sliding within a third (see 

 illustration). The longer tube contained the convex object lens and 

 two diaphragms, while the other held a convex eye lens and had a 

 diaphragm at the eye end. The size of the image could be modified by 

 changing the distance between the two lenses, by means of the sliding tubes. 



Friends of Galileo have claimed that he, not Janssen, was the inventor of the 

 microscope; at any rate it is certain that as early as 1610 Galileo had made one 

 of his telescopes of much shorter focus than were his first instruments, and had 

 used it to examine minute objects, with great astonishment to himself and friends. 

 He reports the possibility of causing a fly to appear as large as a hen, a magni- 

 fication of some thirty-five diameters. 



Drebbel, a Dutch optician, made similar use of the Keplerian telescope in 1621. 

 It will thus be seen that the microscope has come to us as a development of the 

 telescope, and as the power increased it was found, as in the case of the tele- 

 scope, a suitable support or stand must be provided in order to secure the requi- 

 site steadiness for accurate observation. Even some of Galileo's microscopes, not 

 later than 1840, were mounted on tripods through which they were focused by a 

 screw thread on the body just as are our tripod magnifiers to- 

 day. The compound eyepiece was invented by Monconys in 

 1660, a condenser for securing increased illumination by 

 Hooke in 1665, the compound objective by a London opticiark 

 in 1668, and a binocular microscope by Chevalier D'Orleans 

 in 1685. A fine adjustment screw for focusing was applied 

 by Mr. Joblot in his microscope of 1718. The mirror was 

 first used for illumination by Hertel in 1716. The various 

 instruments of this period were of every conceivable design, 

 large, ungainly, highly ornamented and mostly employed for the 

 diversion of kings and nobles. The barrels were of immense 

 size, mostly of wood. Many instruments were two feet or more in height. Ob- 

 jects were mounted between bits of glass held in ivory strips, sometimes half a 

 dozen on a strip. We reproduce an old figure of Hertel's microscope to give 

 an idea of the general tendency in the early days of the microscope. l. b. e. 



