Notes. 573 



coloured minerals, might possibly be produced. The formation of large 

 crystals is then discussed in connection with the work of Tammann, an I 

 finally, the production of large crystals from aqueous solutions, the formation 

 of crystalline substances insoluble in the liquid present, by gradual chemical 

 action between dissolved bodies, and the formation of crystalline bodies by 

 deposition from the gaseous state, are touched upon. In the study of the 

 nature and mode of production of large mineral crystals might well lie the 

 key to further progress in optical materials. 



The Mechanical Design of Instruments. 

 By Walter Eosenhain, B.A. B.C.E. 



This paper is a plea for the contention that in a scientific instrument 

 appearance should be altogether sacrificed to utility. A well-made and well- 

 designed machine tool was the ideal prototype of a scientific instrument. 

 There was frequently a tendency to carry refinements requisite in special 

 cases into general use, which often resulted in a loss of mechanical strength 

 and rigidity. 



The Microscope comes in for a full share of criticism. 



A Simple Pattern of Miohelson Interferometer. 

 By Herbert Stans field, B.Sc. 



Working instructions are given for making in a simple and comparatively 

 inexpensive way an interferometer, with which many educational experiments 

 can be carried out. A special feature of the instrument is the mounting of 

 the various parts on geometric bearings. 



Oct. 18th, 1905 2 Q 



