The Microscope. 



99 



A fragment remains of a wooden arm, one end of which was 

 keyed to the outer rim of the stage, the other free end having the 

 form of the segment of a circle, and having apparently contained 

 originally, at equal distances along the segment, some eight circular 

 perforations, in which objects could be enclosed between glass or 

 mica covers, so that when the arm was moved the objects would 

 pass in succession beneath the objective. 



I have recently found, in the same village and under similar 

 circumstances, another microscope, of the 

 Culpeper type, being the exact counterpart, 

 in every particular, of one figured in Plate 

 IV of Adams's "Essays on the Micro- 

 scope,"* except that the present one has 

 the addition of a rack and pinion for 

 focusing, a decided improvement, though 

 the rack and pinion movement of this 

 instrument is not nearly so satisfactory 

 as that of the screw in the older one 

 described above. 



The accessories to this microscope are 

 precisely as described by Adams, even to 

 the five " ivory sliders with objects," each 

 " slider " containing four objects, one 

 having fish-scales, another vegetable sec- 

 tions, a third animal parasites, the fourth parts of plants, and the 

 fifth various objects. These are mounted dry between thin plates of 

 mica, secured by sprung rings of brass. 



A search in the same locality for early microscopical literature 

 has proved fruitless. 



Economy, Penn. 



NOTE ON A FASOLDT TEST-PLATE. 



From remarks by R. H. Ward, M. D. , at the Pittsburg meeting of the American 

 Society of Microscopists, Sept. 2, 1887. 



^ I HE plate consists of 23 bands ruled on a cover-glass, beginning 

 -*- at 5,000 lines to the inch and increasing by 5,000 each time 

 to 30,000, and thence by 10,000 each time to or toward 200,000. 

 The lines are ruled alternately longer and shorter, so that the 40,- 

 000 band becomes at each end a 20,000 band with interlying lines, 



* Essays on the Microscope, by George Adams, London, 1787. 



