108 MEMORANDA. 



Cheap Achromatic Microscopes. Referring to the last edition 

 of Beale, ' How to w^ork with the Microscope/ I note that 

 on page 10, paragraph 15, Mr. Salmon and Mr. Highly are 

 stated to have been the first in London to bring out a good 

 and cheap Achromatic Microscope. I take it that this 

 remark does mean to confine itself exclusively to London ; if 

 this be so/I beg to inform you that this is by no means correct. 

 My late partner and friend, Mr. A. Abraham, brought out 

 as early as 1841 a very efficient instrument, with two sets 

 of achromatics as powers, these last (the powers) being made 

 by Nachet of Paris, and of which (complete in a case with 

 apparatus) great numbers were sold at £8 retail. I am glad 

 to be able to send you a lithograph of this instrument, with 

 full description, printed at the time named. 



Upon the principle of awarding honour to whom honour is 

 due, I shall be glad if you will insert this in your forthcoming 

 number. — George S. Wood, 20, Lord Street, Liverpool. 



" Slide-Cell," or new Live-Box for Aquatic Objects. In the ex- 

 amination of these objects, which from their numbers and 

 variety are conveniently classed under the term '' pond life,''' 

 I have felt the want of some apparatus which would confine 

 them within a limited space, and yet afford means of watch- 

 ing their habits and processes of development. After em- 

 ploying the different patterns of live-boxes, troughs, &c., 

 which have been recommended, I have found none more 

 useful or better adapted for practical observation than the 

 " slide-cell,''^ and which, for the benefit of my fellow-micro- 

 scopists, I briefly describe. 



By reference to the drawing it will be seen that the ap- 

 paratus can be manufactured for a few pence, and this is, of 

 course, a recommendation. 



Figures 1 and 3 are plan and section views of the '' slide- 

 cell.^' 



A is a glass slip 3 x 1, in the centre of which a circular or 

 oval well is " punted " out in the usual manner. B is a thin 

 glass cover, to one end of which is attached, by shellac or 

 other cement, a brass disc, C, having a frilled edge. A hole 

 is drilled through one end of the slip A, and also through 

 the centre of the disc B. Through these holes is passed a 

 stud pin D, which has a small head at the lower end, the 

 other end being tapped to receive a small nut, E. A thin 

 washer of leather is placed upon the stud D, between the 

 disc and the slip to ensure a proper bite. By unscrewing the 



