208. CORRESPONDENCE. 



course, as the German fashion is, both mirror and cliaphi'agm ; and 

 their conclusions as to the quality of the objective under examination 

 are formed accordingly. 



For my own part, I have for some time adopted a proceeding some- 

 what similar, but infinitely more trying. Instead of straight sunlight, 

 I employ the straight light of a common comjiosite candle, and 

 discard both mirror and diaphragm. 



My i inch (one of Gundlach's earliest issues) will in this way not 

 only do all that I have seen German eighths do, with the help of sun- 

 light, mirror and diaphragm, but do it with greater sharpness and dis- 

 tinctness. I may mention that, when in the summer of 1872 I visited 

 Messrs. Scibert and Kraft's establishment at Charlottenburg, and 

 Herr Seibert showed me the above-mentioned feat with simlight, as a 

 grand tour de force, I took my own ^ inch out of my pocket, and 

 requested Herr Gundlach, who chanced to enter the room at that 

 moment, to try it against Herr Seibcrt's. He did so ; and the result 

 was a complete victory for my glass, to Gundlach's great delight, 

 when I informed him that the glass was one of his own manufacture. 



So much for eighths. 



Well, on Saturday last, L. Beneche of Berlin sent me, as I had 

 requested him, a specimen of his newly improved No. 7, which 

 corresponds to a weak English ^ inch. 



I tried it the same evening, using straight candlelight and a B eye- 

 piece, but without mirror or diaphragm. The test aj)plied was one of 

 Moller's slides of P. angulatum. 



Under these conditions it showed the markings on P. angtilatum 

 with the utmost distinctness, leaving nothing to be desired on that 

 score. Indeed, I preferred its performance to that of my ^ inch, with 

 which I compared it. 



I then took out the eye-piece, and used as an eye-piece a very 

 indifferent 1-inch objective. This method, though resxilting in a per- 

 ceptible loss of light, left the definition as sharp as ever. My ^ inch, 

 on the other hand, broke down completely under this last test. 



Then I proceeded to try Beneche's glass on a variety of other 

 tests, from P. halticum up to S. gemma, and in all cases with excellent 

 results. Its performance on S. gemma I shall leave unrecorded, as 

 the truth here would seem incredible. Meanwhile, its pei-formance on 

 P. angulatum is- a pretty " big thing " for a ^ inch ; and I shall bo 

 glad to hear if any of your readers can do the same with (heir 

 quarters. 



I am yoiu's, &c., 



W. J. HiCKIE. 



