( ^^\A \ r Monthly Microscopical 



(^ lU-i ; L Journal, Feb. 1. 1870. 



COKKESPONDENCE. 



Nobebt's Test-Lines. 



To the Editor of the ' Monthly Microscopical JournaV 



148, Cheapside, E.g., January 12, 1870. 

 SiE, — In p. 283 of the Journal for November last, the reporter 

 of the discussion on Dr. Woodward's paper appears to have quite 

 misunderstood my remarks. I did not say that Messrs. Powell and 

 Lealand had " ruled a test-object with 100 lines in yoVo'" ^^^ch. is a 

 mistake. I expressed a doubt whether the lines on Nobert's test- 

 plate could be clearly defined beyond the 16th group. I added that 

 with Powell and Lealand's new method of oblique illumination the lines 

 on the Amphipleura pellucida and acus could be clearly shown with 

 their immersion ith, ^V*^? ^^^ iV*^' which also give a beautiful defi- 

 nition of the Podura scales. Mr. Lealand has succeeded in counting 

 the Amphijpleura lines, and finds them 100 in xqVo*^ ^^ ^^ inch. 



Ellis G. Lobb. 



Collins' Dissecting Microscope. 



To the Editor of the ' Monthly Microscopical Journal.' 



January 13, 1870. 



Deae Sib, — In reply to the letter of Dr. Swintard, of the New 

 York College of Veterinary Surgeons, I should be glad to explain 

 that if I adopted any plan (invention I did not presume to call it) 

 of Dr. Busteed's it was quite unknown to me; but there is one 

 part of my arrangement that I find much appreciated, and is, I think, 

 novel. 



If the engraving is examined it will be seen that the arm is in two 

 portions ; the lower half with the objectives is fixed, and the upper 

 half carrying the body turns upon a centre, so that it can be instantly 

 converted from a single microscope to a compound, or vice versa. It 

 is also fitted with my new double nose-piece, so that the changes of 

 power can be most easily and quickly effected. 



Before Dr. Swintard's letter appeared, I was engaged in carrying 

 out a suggestion of Mr. Westell's ; this is now nearly completed, and 

 will greatly add to its value as a dissecting microscope, and at the 

 same time remove it from any apparent similarity to that made by 

 Mr. Grunow. 



I am, sir, your obedient servant, 



Chas. Collins. 



