Hagen.] 360 [March 10, 



This instrument costs 390 francs, about $104.00 in currency, and 

 the camera and lens, 50 fr., about $14.00. 



The catalogue sent with the microscope gives numbers of the ob- 

 jectives from 10 to 18, or from Jg to -^^ inch. The ^^ costs 200 

 francs ($53), the -^^, 500 fr. ($134), and the other numbers vary 

 accordingly. 



The two stronger eye-pieces, 5 and 6, cost ten francs each. No. 5 

 magnifies seven and one half times. No. 6 is unknown to me. 



My instrument is number 8066. Nineteen years ago, in March, 

 1850, Prof Vrolik received from the same optician, number 1786. 

 Since then he has delivered 6280 microscopes, 330 a year, or almost 

 one a day. My instrument was received about six months after I 

 ordered it. 



The Section may be interested in seeing an old German microscope 

 made in Berlin by Scheck, in 1837, and used by me for many years. 

 The defining power is even now sufiicient, but the penetrathig jjower 

 in all microscopes at that time was very low. In the old Nobert's test 

 plate of ten bands, it resolved the 6th well, but the 7th is doubtful. 

 At this time Scheck' s microscopes were considered the best by the 

 most experienced observers, especially by Ehrenberg. I am sorry I 

 cannot exhibit a microscope in my possession, nearly two hundred 

 years old, and now in good order. I have watched with great 

 interest the growing demand for these instruments, and the surpris- 

 ing increase in the number manufactured during the last thirty years. 

 Long ago I made my first observations on the scales of Lepidop- 

 tera and Coleoptera, with an old English microscope, perhaps of 

 Martin, and only partly achromatic. Since then I have used first class 

 microscopes of Ploesl, then those of Scheck (none of them is suffi- 

 cient to show the transverse lines on the scales of Lepidoptei'a), later 

 of Oberhauser and Nachet. 



From this time almost every European naturalist gave up using 

 microscopes mounted upon high stands, as observations with high ob- 

 jectives are more easily and accurately made in a sitting position, 

 when the arms can be supported upon the table. The end is not 

 attained by placing a microsot|)e with a high stand upon a low table, 

 because the hands are less readily guided at a distance from the 

 eyes. The English opticians appreciated this, and arranged a strong 

 wooden transverse rest for the hands, even in single microscopes. 



I have noticed that foreign students entering the Institute for Path- 

 ological Anatomy, very soon exchange their high-stand, English mi- 



