878 EECORD OF CURRENT RESEARCHES RELATING TO 



a still further improvement, yet the performance of the eye-piece 

 leaves little to be desired. The wavy, basket-like, longitudinal strise 

 on Surirella gemma and the hexagons on P. angulatum are well seen 

 with a \ objective, and the Frustulia Saxonica and A. pellucida (dry) 

 have been resolved by it with a non-adjusting ^ of Gundlach's. 



In place of the concave meniscus referred to, I have also used, 

 with nearly as good effects, a double concave lens of 2 or 3 inches 

 equivalent focus, such as can be obtained at an optician's for about 

 50 cents. So that by a very small cost of time and money, the pos- 

 sessor of an ordinary objective may increase the power of his instru- 

 ment to a very great degree. 



I reiterate the conviction before expressed, that further improve- 

 ment of the Microscope may be looked for in the construction of eye- 

 pieces — regulating their magnifying power and increasing their 

 diameters so as to concentrate rays from the objective, which are now 

 absorbed by the sides of the tube." 



Foreign Mechanical Stages. — We described and illustrated at 

 pp. 712-13 (Figs. 60-1) a mechanical stage (by Schmidt and 

 Haensch), which was claimed to be a great improvement uj)on other 

 stages, and the action of which, as regards the movement of the 

 object in two rectangular directions, and the proof that thereby every 

 part of the object must certainly come into the field of view, were 

 given with extreme minuteness, as if the idea of a mechanical 

 stage with rectangular movements had only now dawned upon 

 microscopists. 



The matter has now been carried a step further, and we are 

 brought somewhat nearer to the present day by the two stages 

 described below, and which are represented to be better than the 

 English stages in several important particulars. As the descrip- 

 tion * wonld suffer by any abstract, we have given a full translation. 

 The writer (Dr. E. Kaiser, of Berlin) first refers to the above Micro- 

 scope of Schmidt and Haensch.j and its arrangement for exact 

 centering of the tube whilst focussing, and then proceeds as 

 follows : — 



" We Germans have hitherto fitted up our Microscopes in a most 

 meagre way as regards mechanical accessory apparatus. If we compare 

 our instruments in this respect with those made on the other side of 

 the Channel, we must certainly confess that ours are far excelled by the 

 English ones. We have always consoled ourselves for this with the 

 idea that the numerous mechanical appliances of the English instru- 

 ments are really only playthings which are never in any case necessary. 

 But nothing is so erroneous as this idea. The so-called ' substage ' 

 of the English, their provisions for the fine adjustment and me- 

 chanical motion of the object, do not constitute a mere plaything in 

 any sense, but are absolutely necessary and indispensable for scientific 

 investigations. The conviction of this has gained ground with time 

 more and more in oiu' scientific circles, and to Zeiss's manufactory, 



* ' Bot. Centralb].,' i. (18S0) p. 728. t See this Journal, ante, p. 713. 



