I. APPARATUS, ETC. 745 



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.) 



3439. Support for Crystal in the ordinary Wollaston Gonio- 

 meter, on an improved principle. 



Professor Jos. P. O'Reilly, Dublin. 



This support is completely detached from the axis when the crystal is 

 being mounted, offering, therefore, the greatest facility for this operation ; it 

 also brings the crystal outside the end of the axis, so that no part of the 

 support can intervene between any face and the mirror underneath it. 



343 9a. A Simple Substitute for a Goniometer. 



Professor W. H. Miller, Cambridge. 



By means of this a crystal can be measured by Wollaston's method, and 

 the angle of an edge determined by the determination of the angle between 

 two lines drawn on paper along the wooden part of the instrument in its two 

 different positions, by comparing the arc, intercepted by the two lines on a 

 circle drawn through the point of intersection of the lines, with the whole 

 circumference by means of compasses. 



3440. Goniometer, with additional pieces of apparatus, by 

 which it may be converted into an instrument for determining 

 refractive indices, and an instrument for measuring the angle 

 between the optic axes of biaxial crystals. 



University of Oxford. 



3441. Contact Goniometer, being the instrument used by 

 the Abbe Haiiy. University of Oxford. 



It was formerly in the collection of Haiiy's minerals, acquired by the late 

 Duke of Buckingham. His Grace presented it to Dr. Buckland, by whom 

 it was placed with the collection of minerals belonging to the University of 

 Oxford, in which Dean Buckland was professor of mineralogy and geology. 

 The Dean's autograph is on the morocco case. 



3442. Goniometer, with horizontal circles, and adjusting level. 



Professor Baron von Feilitzsch, Greifswald. 



This reflective goniometer has a dividing circle, of 7 5 inch diameter. 

 The division runs direct as far as ^, and with the application of the nonius 

 5 minutes may be read. The instrument can likewise be used for spectrum 

 experiments. 



3443. Goniometer. JR. Fuess, Berlin. 

 3443a. Goniometer. M. Lutz, Paris, 

 3443b. Goniometer, Wollaston/ M. Lutz, Paris. 

 3443c. Goniometer, Babinet's. M. Lutz, Paris. 



3444. Reflecting Goniometer, on marble slab, in maho- 

 gany case. Georg Breithaupt, C asset. 



