114 JOURNAL OF THE [October, 



one of plate-glass, the focusing of the image being accomplished 

 by the aid of a magnifier. 



4. The Objective. The ordinary microscope-objective was 

 not desirable. Because in it the visual and chemical foci were 

 not coincident, although it could be used, by making the neces- 

 sary allowance after focusing the object, which allowance could 

 be ascertained by experiment. An objective especially corrected 

 for this work would be found much more satisfactory. 



By the use of the lantern, a series of views, illustrating the 

 development of the construction of various forms of apparatus, 

 was projected upon the screen and explained. These illustra- 

 tions had been secured by using a portrait-lens, when a low 

 magnification was desired, and Carbut's "B" plates, with the 

 pyro. or oxalate developer, and also orthochromatic plates in 

 special instances. 



Prof. Louis H. Laudy then addressed the Society upon the 

 use of the Arc-Electric Light, in the projection of the images of 

 microscopic objects, detailing the difficulties to be surmounted. 



After explaining the working of the apparatus. Prof. Laudy 

 gave a demonstration of the superiority of this method of illumi- 

 nation. By way of comparison, projection of the image of a 

 microscopic object was made to alternate with that of a lantern- 

 slide of the same object, shown with the lime-light, to the mani- 

 fest advantage of the arc-light, even under these trying 

 circumstances. 



This alternate projection of the images of object and lantern- 

 slide served forcibly to illustrate the relative actinic and non- 

 actinic properties of certain colors in the object, and the cases 

 in which the orthochromatic plate could be used to advantage. 



A large number of photomicrographs, representing a great 

 variety of subjects, were also exhibited for inspection. 



Meeting of May 17TH, 1889. 



In the absence of the President and the Vice-President, Mr. 

 J. D. Hyatt was elected Chairman. 



Twenty persons present. 



The Microscope — A Zentmayer Army-Hospital binocular 

 stand — donated to the Society by the late Benjamin Braman was 

 brought to the Society's rooms by Mr. John L. Wall. 



