212 PROCEEDINGS OF SOCIETIES. [*^™Jnil AprllTim 



mounterl above the ordinary eye-piece of the microscope by means 

 of a tube adapted (taking the place of the eye-piece cap), in which 

 the prism tube will slide. An adjustable slit is made to take the 

 place of the micrometer in the eye-piece. When a second or com- 

 parative spectrum is required, it is only necessary to place below the 

 object-glass either a " Eeade's " or a right-angled prism, or a simple 

 reflector, and the two spectra will appear side by side. By this 

 arrangement all the advantages of the more expensive forms of in- 

 struments are obtained at a small cost. It was as well a spectroscope 

 for non-microscopic work. 



A new form of rotating stage of portable character was exhibited 

 by Mr. Blankley, and also a very convenient pocket travelling micro- 

 scope by Mr. Browning. This very portable form of instrument was 

 made for a gentleman connected with the Excise, who, being much 

 engaged in the examination of suspected articles, is obliged to carry 

 a microscope about with him in his daily duty. 



IVIi-. Moginie also exhibited his monocular and binocular travelling 

 microscopes ; and Mr. Eichards his arrangement for working more 

 accurately with Barker's selenite films. 



Dr. Carpenter compared " The Steadiness of the Eoss and Lister 

 Models of Microscopes under trying circumstances." He also entered 

 into some interesting details " On the Shell-Structiu'e of Fusulina," 

 " The Micropyle of the Fish's Ovum," and " The Eeparation of the 

 Spines of Echini." 



Mr. Beck thought the real credit of carrying out the principle so 

 ably commented upon by Dr. Carpenter belonged to Mr. Jackson. He 

 did not think that in Mr. Lister's improvements would be found the 

 full development of the principle. He had in his possession the first 

 microscope that had been made on Mr. Lister's model, as brought out 

 by Tulley ; and whilst the princijjle is firmly maintained of moving 

 the body, there is no approach to the beautiful movement for which 

 they were indebted to the mechanical skill, and thorough knowledge 

 and distribution of vibration, of Mr. Jackson. George Jackson was 

 the man who introduced the planing out that arm ; and he thought 

 that he was correct in saying that it was planed out by Mr. Jackson 

 in an amateur planing machine of his own. 



The President said Tulley 's microscope was the Lister model. 

 The supporting rods gave gi-eat firmness, but the form exhibited by 

 Dr. Carpenter was unquestionably the Jackson form. Still the ques- 

 tion is, which form is the most valuable for diminishing the tremor ? 



Mr. Breese said, it seemed to him that the question of vibration 

 must be mainly dependent upon the steadiness of the object-glass and 

 object taken relatively, and consequently on the rigidity between these 

 parts, and had but little to do with the eye-piece, as spoken of by 

 Dr. Carpenter. He would contend that the Eoss model is the steadier 

 of the two. The point of support for the object-glass is much nearer 

 the object, and tliere is no danger of motion in the tube interfering at 

 all. Without calling in question the experiments made by Dr. Car- 

 penter, he thought that a Eoss model, which he had had in his own 

 hands, bore as severe a test, and exhibited no defect such as has been 



