268 PROCEEDINGS OF THE SOCIETY. 



to make in each case a central intercostal line. The orientation of the 

 grating being maintained unchanged, a series of paired lines is now 

 viewed with the unaided eye, the search being continued until a pair of 

 lines is found which again vields a median intercostal line. 



The linear interval between the paired lines in question is measured 

 and is divided by the linear interspace between the lines on the Abbe 

 diffraction grating. The quotient gives the magnifying power of the 

 Microscope. 



New Fellows. — The following were elected Ordinary Fellows : — 

 Messrs. Frederic John Cheshire, Kenneth Weldon Coadby, Cyril Francis 

 Hill, Dr. John Eennie, and Rev. Carlos Zimmermann. 



