712 



APPENDIX. 



from fatigue belonging to the use of this form of miscroscope ; 

 for when placed on a table, rather higher than the one commonly 

 used, and a foot or two from the edge, the observer can recline 

 on his arms, and observe for hours without the slightest sensa- 

 tion of fatigue.^ Messrs. J. & W. Grunow, ]^ew Haven, Conn., 

 are the manufacturers of this instrument. 



DR. J. LAWRENCE SMITH'S GONIOMETER AND MICROMETER. 



Professor Smith has also invented a Goniometer for measur- 

 ing the angles of crystals under the microscope. It is also com- 

 bined with a Micrometer. The following is a description of the 

 instrument with the method of using. (Figs. 433-4.) 



H is the upper end of the draw-tube of the microscope, with 

 the ring k soldered to it. Over this ring k, screws another ring 

 F, which serves as a support and as a centre to the graduated circle 

 D, which freely, but without shaking, revolves upon the same. 

 Into the bore of the ring F, fits by its lower conical end h, the 

 tube Cr, which is held in it by a screw-ring ^/, that prevents its being 

 taken out. Into the tube G, which also has a free revolving 

 movement, fits the positive eye-piece a, d being the field-lens, 

 s the eye-lens. 



The slide b b, on opposite sides of Cf, admits of the micrometer 

 with its mounting £, B being introduced into Cr, and the gradua- 

 tion being brought into the field of the eye-piece. 



Fig. 433. 



C is an index, attached to G by the screw c ; it may be taken 

 off, when the apparatus is not used as a goniometer. 



' See American Journal of Science and Arts, for September, 1852, in which the 

 entire paper of Prof. Smith will be found. 



