394 JULIUS RHEINBERG OX STEREOSCOPIC EFFECT. 



It is interesting also to note that in stereoscopic photo-micro- 

 graphs we are able to correct for perspective distortion subse- 

 quently in Beveral ways: — 



1. We may use weaker or stronger lenses in the stereoscope. 



2. We may increase or decrease the distance between the same 

 stereoscope lenses. In the former case we are looking through 

 th< in Dearer the margins of the lenses, which has the effect of 

 flattening the picture. 



3. We may decrease or increase the distance between the two 

 pictures, the former flattening, the latter deepening the picture.* 



Photographs of the minute spherical foraminiferal shells 

 Orbulina have been taken by Mr. Taverner under all sorts 

 of varying conditions — i.e. with the stops above or below the 

 objective, variously placed. In the correct photographs the 

 shells are seen nearly truly spherical ; in others they appear to 

 be ovals of considerable depth. The same photographs, however, 

 change in appearance as the distance between them is altered in 

 tln> stereoscope, or as the distance separating the stereoscope 

 Lenses is changed, as indicated above. f 



In conclusion, I must express my best thanks to Mr. Charles 

 Baker and to Messrs. Carl Zeiss for their kindness in lending; 

 apparatus, and to Mr. Taverner for the experimental photo- 

 graphs taken to illustrate the various points. 



paper on "Stereoscopic Distortion," by Lyndon Bolton, F.R.A.S., 

 in the Photographic Journal, vol. xliii., No. 4, April 1903. 



t One of Mr. Taverner's photographs of Orbulina, and several other 

 Btereoscopic photos, are reproduced on Plates 22, 23, and 24 of the last 

 number of this Journal. 



Microscopical Club, Ser. 2, Vol. IX., No. 59, November 1906. 



