the coarse adjustment until the image appears. Use 

 fine adjustment. 



It is also advisable while watching for the image 

 to appear to move the object slightly in different direc- 

 tions, as the flitting of shadows or colors across the 

 field will give indications that the objective is nearing 

 the focal point. 



Always focus upward. In case a low power is 

 exchanged for a higher power objective or when the 

 low power has been used as a searcher, i. e., to find a 

 certain object in a collection or a certain locality on a 

 specimen, the tube should first be elevated as the 

 working distance in the high power is too short to 

 admit of screwing it into the nose-piece, then detach 

 the low power, attach the high power and proceed to 

 focus in the order given. 



The method of procedure with the revolving nose- 

 pieces, either double, triple or quadruple, is different. 

 The writer believes he was the first to establish the 

 commercial possibilities of making two and more objec- 

 tives in revolving nose-pieces par focal, i. e., to so 

 adjust the focus of each objective that when either 

 one in swung into position it is nearly focused and 

 requires the use of the fine adjustment only. This 

 feature not only adds to the comfort of using objec- 

 tives, but facilitates work and removes the danger of 

 objectives coming in violent contact with the cover 

 glass. Very low power objectives vary from those 



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