CORRESPONDENCE. 



275 



the value of tLc beaded appearances on wliicli was based an attack on 

 our observations and objectives, wbich is still, in my opinion, most 

 insufficiently sui)2>orted. 



I will not now do more than express a hope that Dr. Pigott's 

 record of personal observations is more precise than his statement of 

 facts. 



I am, dear Sir, faithfully youi-s, 



Jno. H. Hennah. 



Mr. Ross's Objectives. 



To the Editor of the ' Monthly Microscopical Journal.' 



Gkove House, Newbold Steeet, Leamington, Aj^ril 4, 1872. 

 Dear Sir, — To the numerous readers of the Journal who, like 

 myself, look out for its successive ajipearances with expectation and 

 pleasure, perhaps this note may not be without its interest. I have 

 no doubt we all feel a degree of justifiable pride in the name of 

 Ross, as historically connected with the achromatic microscope, and 

 regret the loss of father and son, who kept so well to the front in the 

 constant march of improvement. I am hapjjy to say there is every 

 probability of the old House keeping uj) its well-earned reputation. 

 A few days ago I received a box of objectives from the present firm, 

 which were so superior that I feel it to be only an act of justice to 

 call attention to them. The y^^ths surpassed any other glasses of 

 like focus I ever received from them, and we all know how T. Ross 

 prided himself on this combination : the beauty of their performance 

 was equalled only by their facile resolution of tests ever considered 

 difficult for this power. Another glass of remarkable character and 

 excellence was a " new " ^th, which acts most beautifully as a dry 

 lens, and by manipulating the adjustment, ivitliout change of front, per- 

 forms admirably as an immersion lens. This double performance as 

 dry and wet lens is shared, as far as I know, only by Powell and 

 Lealand's beautiful ith. This ith resolves the Cymatopleura elliptica 

 of Moller's Probe Platte. I would here remark that Mciller having 

 used such a thick slide to mount the diatoms on, prevents the proper 

 illumination requisite to bring out the best results. I found by 

 gently warming the slide I could remove the cell containing the 

 diatoms. This I did, and remounted it on very thin glass, with the 

 best result, and without disturbing in the least the beauty or perfec- 

 tion of the test-j)late. All Eoss's glasses, I understand, are now 

 worked from new formuh^, which promise a still further point of 

 excellence : they have a new y^jth under construction, from which 

 much is expected, and no doubt justly so. 



I am yours truly, 



Thomas Biet, M.D. 



