I. APPARATUS, ETC. 885 



3431. Collection of Minerals for Blowpipe experi- 

 ments. Royal Mining Academy, Freiberg, Saxony. 



3432. Illustrations of Metallic Incrustations produced 

 by means of the blowpipe on charcoal, by Dr. Theodor Richter. 



Royal Mining Academy, Freiberg, Saxony. 



3433. Harkort's self-made Scale for measuring small 

 Globules of Silver. 



Royal Mining Academy, Freiberg, Saxony. 



b. GONIOMETERS, &c. 



3433a. Double-refraction Eyepiece Goniometer, for 



measuring angles of crystals in the microscope. 



University of Oxford. 



On the construction of the late Dr. Leeson, and given by Mrs. Leeson to 

 the University of Oxford. 



3434. Retort and Geissler Tube, used by Prof. Vogelsang 

 in his experiments, proving the liquid contents of certain minerals 

 to be carbonic acid. 



Royal Polytechnic School, Delft, Prof. J. Bosscha. 



3435. WoIIas ton's. Reflecting Goniometer, with an 

 arrangement for readily centering the crystal ; also a portable pair 

 of adjustable bright signals, the spot being reflected from the 

 crystal, and the line from a black mirror placed underneath it. 



Charles Brooke, M.A., F.R.S. 



3435a. Reflecting Goniometer, invented and used by Dr. 

 W. H. Wollaston. Accompanying it are notes of some of his 

 measurements of crystals. G. H. Wollaston. 



3436. Wollaston's Reflecting Goniometer, belonging to 

 and used by the late Rev. Dr. Whewell, D.D., F.R.S., Master of 

 Trinity College, Cambridge, when Professor of Mineralogy. 



Rev. Nicholas Brady, M.A. 



3437. Babinet's Goniometer, for measuring angles of crys- 

 tals and refractive indices of liquids. For the latter purpose the 

 liquid is placed in the hollow prism. Frederick Guthrie. 



3438. Working Model of a new and simple form of Reflec- 

 tion Goniometer, very compact, and allowing the application 

 of a vernier for exact measurement. Prof. Jos. P. O'Reilly. 



In this model a spiral traced on a cylinder is substituted for the divided 

 circle, as in the ordinary Wollaston. The measurements are given by the 

 intersections of the spiral with a divided straight edge parallel to the axis of 

 the cylinder and in contact with it. 



See Plate accompanying notice ; Proc. Roy. Irish Acad., ser. II., vol. I., 

 pi. XX. (The model represents the first form, since modified as in the plate.) 



