INDUSTRIAL PROGRESS DURING THE YEAR 1875. cxxxv 



changed one into the other, it becomes a question of much 

 interest to consider whether, when we meet spectra having 

 similar relations, the substances may not be in some way 

 connected, although it may be impossible to convert one 

 into the other. Mr. Sorby gives several striking examples of 

 these equal ratios, though the actual wave-lengths are very 

 different, produced by different coloring matters, and which 

 appear to show that some simple but unknown molecular 

 or chemical combination really exists between them. 



A self-centring turn-table, by Mr. C. F. Cox, is described in 

 the March number of the Monthly Microscopical Journal, 

 which will meet a want often felt by those who bestow any 

 care upon neatly mounting their preparations, and especial- 

 ly when cells are to be prepared for reception of opaque ob- 

 jects. 



In the August number of the Journal of the Quekett Mi- 

 croscopical Club is a description of an ingenious arrangement 

 for cleaning very thin covers without breaking them. It con- 

 sists of a small tube of brass or steel, about an inch in diam- 

 eter, and the same in height, into which fits loosely a weight- 

 ed plug. To the lower end of this plug is cemented a piece 

 of chamois leather. Another piece of leather is stretched 

 upon a flat piece of wood or plate glass to form a pad, which 

 completes the apparatus. The tube being placed upon the 

 pad, the moistened thin cover is dropped into it, and the 

 weighted plug placed on it ; holding the tube well down on 

 the pad, one can rub as much as necessary without any 

 danger of breaking, the weight of the plug giving sufficient 

 pressure to clean the glass. The manipulation is quite easy, 

 and it is difficult to break the glass. 



Mr. Wenham describes in the April number of the Monthly 

 Microscopical Journal a new " Method of obtaining Oblique 

 Vision of Surface Structure under the Highest Powers of the 

 Microscope." He advises the use of slips of glass about four 

 tenths of an inch wide, ground and polished at an angle at 

 one edge. The object to be examined is placed upon the 

 sloping plane. One of the slips is cemented to the ordinary 

 three-by-one-inch slide, and the other slip being slid against 

 it, the object will lie flat between the two inclines. It is nec- 

 essary to have the two inclines to remove the objectionable 

 color which would otherwise enter into the objective. He 



