1883.] modifications of Soret's fluorescent eye-piece. 



343 



for seeing the fluorescent light while stray light would be re- 

 fracted out of the line of vision. Eye-pieces on this plan have 

 accordingly been made for us by Hilger, one with a thin wedge 

 of uranium glass and others with a wedge-shaped vessel of which 

 the side next the object-glass is a plate of quartz, and on the 

 inner face of this the pointer is placed. The side of the vessel 

 next the eye-lenses is of glass, and the vessel is filled with a 

 solution of sesculine made slightly alkaline with ammonia. The 

 body of the vessel is of brass, and there is a small window closed 

 with glass at the bottom through which light may be thrown on 

 the pointer when necessary. 



f l ¥=r mm 



The figure shews the eye -piece in section, a is the quartz 

 plate, b a glass plate, d the window closed with glass, c the hollow 

 which is filled with aesculine solution through a hole at the side 

 which is closed with a screw plug with a minute perforation. The 

 eye-lenses must be adjusted to the proper distance for distinct 

 vision of the inner face of a before the eye-piece is inserted into 

 the telescope. 



(3) On a spectrometer and universal goniometer adapted to the 

 ordinary wants of a laboratory. By Professor Liveing. 



The instrument exhibited to the Society was designed for use 

 as a spectroscope, for the measurement of refractive indices and 

 generally for all purposes in which angular measurements are 

 required. Its chief features are first the steady support given to 

 the telescopes by the peculiar form of the brackets which carry 

 them. Each bracket has a vernier, and the telescopes can be 

 brought up to one another as close as the diameters of the object- 

 glasses will allow. Above the circle is a turn-table provided with 

 a vernier which can be moved through the whole 360° without 

 interfering with the telescopes, so that the angular motion of any 



