276 THE AMEEICAN MONTHLY [December, 



Leeuwenhoek. 1673; Bonanni, 1691 ; Hartsoeker, 1694; Musschen- 

 broek, 1702 : Marshall, 1704 ; Adams, Cidpeper, ante 1738 ; Cuff', 1740, 

 and Dolland, 1790- 



To those of you who are not familiar with drawings of the very early 

 forms of microscopes, it will be interesting to observe the various models 

 of instruments, and you will be readily convinced that the opticians of 

 those days had a very imperfect idea of the requirements of the micro- 

 scope. Descartes " Galilean" microscope, 1637, and one of 1657, ^§~ 

 ured in Schotts' Magia Universalis and Divini's, same date, are 

 very curious forms, and apparently measure from three to four feet long, 

 while the eye-glasses are said to have been as broad as the palms of a 

 man's hand. These measurements are vague, but sufficiently suggestive 

 to convince one that it must have been a formidable instrument. 



During this period the progress was very slow, and the different 

 forms appear to be, more or less, a reproduction of the others. Very 

 little original work can be shown, and as Mr. Wilson, in his history of 

 the inicroscope, observes, this tends to show '• that the instrument was 

 seldom sufficiently used to show its weak points, while little improve- 

 ment seems to have been made in the definition of the instruments." 



Fontana, of Naples, claims to have made microscopes in 161S, and 

 even as early as 1592. Hufnagel (George) has published a work on 

 the insects, with copper dlustrations. which must have necessitated the 

 use of some high-power lenses. 



The next microscope I would mention is a very pretty compound 

 microscope by Giuseppi Campani, and antedates 1665. Campani was 

 an optician of considerable note, and this instrument is dated as preced- 

 ing Robert Hooke's, 1665, because it has no field lens to the ocular. 

 As Campani would not have neglected so important a feature after its 

 publication, it is safely assumed that his instruments were constructed 

 before 1665. 



The bodj'-tube of this instrument is of ivorj-, screwing into a ring of 

 bone. This is mounted within a silver ring connected with three silver 

 scroll legs coming off' from a base of ebony. It is about 12 inches high 

 wben extended. The instrument bears the name of Campani, and I 

 would add, in passing, that it is a tradition in the museums of Italy that 

 Campani put his name on all of his microscopes. This form of micro- 

 scope is considered a beautiful example of an early Italian microscope. 



The year 1665 brings us to a specially interesting period in the his- 

 tory of this great instrument. 



The publication of Hooke's •' Micrographia " and the suggestions 

 contained therein all point to his practical ability in the use of the mi- 

 croscope. He has described and illustrated a very great number of 

 objects as seen through the instrument of his day, and describes, also, 

 his method of constructing high-power lenses. 



Some authorities are of the opinion that he was the, first to apply the 

 ■field lens to the eye-piece, but in the notice of Huyghens, in the Bibli- 

 ographie Univei'selle^ it appears that Huyghen's had applied this to his 

 telescopes previous to 1659, and this is prior to Hooke's work about 

 six years. 



Hooke was, it is thought, the first to describe a method of estimat- 

 ing the magnifying power of the compound microscope and must be 

 credited with the first suggestion of immersion lenses. He was the 



