80 JOURNAL OF THE [July, 



herein in reference to its being of miocene age. However, if the 

 clay is not of miocene age, it can be so put provisionally until 

 other proof is adduced to the contrary." 



OBJECTS EXHIBITED. 



1. A substitute for the camera lucida: by H. G. Piffard. 



2. A microscopical electric illuminator : by H. G. Piffard. 



3. Arranged spines of Echiims: by H. G. Piffard. 



4. A Zentmayer portable microscope : by Walter H. Mead. 



5. A simple form of compressor : by Walter H. Mead 



6. A Tolles micrometer ruling: by George S. Woolman. 



7. A Rogers micrometer ruling ; by George S. Woolman. 



8. A home-made dissecting microscope : by F. W. Leggett. 



9. A Beck microscope lamp : by Charles S. Shultz. 



10. An enlarged model of Smith's vertical illuminator : by 

 Charles S. Shultz. 



11. A metric scale, ruled by Prof. W. A. Rogers on speculum 

 metal, shown by means of the Beck lamp and the vertical illumi- 

 nator : by Charles S. Shultz. 



12. Aselhis aquaticiis.Xw'vsx'g-.hy Yi^^'sci C. Bennett. 



13. Sections of spines of Echinus: by James Walker. 



14. Automatic revolving stage : by James Walker. 



15. Automatic revolving polariscope: by James Walker. 



Dr. Piffard explained his substitute for the camera lucida — a 

 right-angled prism fitted in place of the eyepiece of the micro- 

 scope, through which the image is projected downward perpendic- 

 ularly upon the drawing paper lying upon the table; also his 

 electric illuminator — a cylindrical glass bulb, three inches in 

 length by one inch in diameter, the illuminating filament, of the 

 ordinary horseshoe form, being composed of copper wire, with 

 the exception of three-quarters of an inch in-length of the middle 

 portion of one limb of the horseshoe, which portion consists of 

 carbon. This carbon, when incandescent, gives a streak of 

 light of intense brilliance about three-quarters of an inch long 

 and apparently about one-eighth of an inch wide. The magnified 

 image of this, focussedupon the object, gives '^ critical" illumina- 

 tion. Diffuse illumination is obtained by racking the condenser 

 a little out of focus. 



Mr. Mead described his exhibits — a Zentmayer portable micro- 



