187 



copists with samples of his fine ruling on glass which has been 

 already noticed in the Naturalist. The lines, which excel any 

 with which we are familiar except the Nobert lines, are now ruled 

 from to inch, on glass slips 3x1, and covered with thin 



glass. They cost $8 or less, according to fineness. 



The Argand Burner. — Microscopists who use illuminating 

 gas with the common Argand burner will be interested in Mr. 

 John H. Martin's suggestion of placing a thin piece of mica, with 

 a small hole punched in its centre, upon the top of the glass chim- 

 ney. A more perfect combustion of the carburetted hydrogen is 

 secured, giving a very steady flame, and the full amount of light 

 with the gas turned about half off. 



Monochromatic Sunlight. — Instead of a small disk of blue 

 glass which has long been used in connection with a shutter or 

 diaphragm or with some illuminating apparatus, Mr. J. E. Smith 

 recommends a blue glass pane of about 12x18 inches, standing 

 at the edge of the table, between the microscope and an open win- 

 dow through which the direct sunlight enters. The pane is sup- 

 ported by a cleat, so that it can be instantly placed in position 

 or removed. The whole instrument stands in the blue light, and 

 is managed exactly as with ordinary diffused daylight. 



Amphipleura pellucida. — The latest measurement of the 

 striae of this favorite "test" is that of Prof. E. W. Morley, of 

 Hudson, Ohio, communicated to the Memphis Microscopical So- 

 ciety, which estimates the markings at 92,600 to the linear inch. 



Professor Ludwig's Jubilcium or the celebration of the twenty- 

 fifth year of his professorship, took place at Leipzig, October 15. 

 This eminent teacher, founder of the Saxon Physiologische An- 

 ; . - 



and fifty private students, whom he has trained in special investi- 

 gations, and of whom many have since become distinguished pro- 

 fessors. There was a large assemblage of friends and pupils to 

 take part in the ceremonies, including Professors Ernst Heinricb 

 Weber, the Nestor of physiology ; Helmholtz, Du Bois Reymond, 

 and others of less fame from Upsala, Moscow, Edinburgh, Brus- 

 sels, Vienna, etc. The oldest scholar proved to be Professor Fick, 



