16± THE AMERICAN MONTHLY [July, 



EXTRACTS FROM CORRESPONDENCE. 



White's Botanical Sections. By E. C. Hoyt, Detroit, Mich. 



Friend Smiley : Although directly antagonistic to my advertise- 

 ment and desire to dispose of a few surplus slides, I am too good a 

 friend of the cause to refrain from saying that you have done more to 

 make yourself popular in selling these prepared sections than you realize. 

 They are simply grand, and anyone is foolish to buy prepared mounts 

 in the botanical line at over 10 cents each. I have spent hours adver- 

 tising these preparations for love of the cause. 



The Journal for June : Postal Club Reports. By S. Lockwood, 

 Freehold, N. J. 

 Permit me to say that the current number is admirable. I am glad 

 that in the race of competition the Journal shows such good wind. 

 I hope the racy sketches on the Postal Club by Queen Mab will be 

 kept up, and not the least interesting is the simple record you are in 

 this way giving of the modest notables who have gone to the waiting 

 land. 



Instantaneous Changes of Field. By Wm. Lighton, Leavenworth, 

 Kans. 



I have made quite a valuable discovery lately in connection with wide- 

 angle homogeneous immersion lenses. By means of a very simple piece 

 of apparatus instantaneous changes from dark field to light field and 

 back again are obtained "with the largest numerical aperture possible, 

 and works equally well with dry lenses of any power and aperture. 

 The effects obtained with it are wonderful, and are obtained without 

 altering any adjustment of the microscope. 



Would you like a drawing and description of it for the Journal ? 

 \_Tesl — Editor.] It is quite likely Messrs. Watson & Sons, of Lon- 

 don, will take it in hand. 



The H. R. Spencer Optical Compa?zy. By H. R. Spencer, Cleve- 

 land, Ohio. 

 We take pleasure in announcing that the firm of H. R. Spencer & 

 Co. is dissolved by mutual consent, and the business is reincorporated 

 as the " H. R. Spencer Optical Company, of Cleveland, O." It is in 

 reality a material expansion of the business so long established. It is 

 our intention to supply a most complete line of microscope objectives 

 for general work, as well as those adapted to special lines of research, 

 and any inquiry or application for advice relating thereto will be cheer- 

 fully answered. Continuing the manufacture of the celebrated micro- 

 scopic objectives, we would announce our greatly increased facilities 

 for the manufacture of telescope objectives from the formulae devised 

 and worked out by the late C. A. Spencer and Herbert R. Spencer, 

 the results of which have received such high commendation from as- 

 tronomers and opticians. 



Information for Scientists about to Visit the Paris Exposition. By 

 J. W. Queen & Co., Philadelphia, Pa. 

 We have representatives in Paris who have had the experience of many 

 years in the selection and purchasing of scientific apparatus of every 



