THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FIFTH SERIES.] 



AUGUST 1895. 



X. On the Use of the Globe in the Study of Crystallography. 

 By J. Y. Buchanan, F.R.S* 



rVMIE use of the globe in Crystallography is twofold. It 

 -L enables us to study the character and follow the details 

 of the form of the solid projected radially on its surface. 

 Also all the measurements which can be made on the solid 

 itself can be as conveniently made on its projection on the 

 sphere, and all calculations and developments connected there- 

 with can be made by simple graphical construction and mea- 

 surements on the sphere. The black globe, with the divided 

 circles belonging to it, is a calculating machine adapted to 

 the solution of all the problems to which the analytical 

 methods of spherical trigonometry are usually applied. 



To the student of crystallography, of astronomy, of 

 mathematical geometry, and of geometry of three dimensions 

 generally, the globe and its circles fill the same place as the 

 drawing-board and scale do to the engineer and surveyor. A 

 globe which is to be used for geometrical constructions should 

 be quite free and unencumbered with the fixed axis usually 

 met with in those intended for geographical or astronomical 

 instruction. Also the divided circles with which measure- 

 ments are made should be capable of being applied directly 

 to the surface of the globe, so as to avoid errors of parallax. 

 The globe which I have found most suitable for the purpose, 



* Read before the Chemical Society, December 6, 1894. Communi- 

 cated by the Author. 



Phil. Mag. S. 5. Vol. 40. No. 243. Aug 1895. M 



