and Laboratory Methods. 



1571 



and it becomes a difficult task sometimes to determine when the instrument is 

 in focus. Often the developed plate shows the unexpected, and failure is the 

 result. 



A long focus lens will, of course, produce results similar to those here given, 



Fig. 4. — Sin-yale-a-min Mountain, Mission Range, Montana. 



but on a smaller scale. The advantage of a telephoto attachment is that the 

 magnification may be made such as will bring out the features desired. With a 

 telephoto attachment, with magnification up to eight diameters, an ordinary lens 

 is increased in value many fold. With a long focus or short focus lens but one 



Fig. 5. — View of Portion of Fig. 4, magnified eight diameters. Plate accidentally reversed. 



size of photograph may be taken, that of the long or short focus. With tele- 

 photo attachment the focus may be lengthened, and the size of the image cor- 

 respondingly increased, at pleasure, resulting in a very great increase in the 

 usefulness of the lens. Morton J. Elrod. 



University of Montana. 



