91 



The principal consideration is whether the instru- 

 ment is to be used in an upright or inclined position. 

 If the former, the short tube is most usually selected, 

 as it can be used comfortably on a table of ordinary 

 height. This one objection which might be and often 

 is raised against the long tube is easily overcome by 

 the friends of the latter providing a suitable table for 

 the same. As the instrument is used in the upright 

 position only in a few special lines of study, it is 

 really only of weight in this direction, as the instru- 

 ment may be inclined to the most comfortable point, 

 and when so is more comfortable than the upright 

 position. 



The joint for inclination of arm is generally con- 

 ceded to be an advantage. While it may be the case 

 that many of the upright instruments are in use in 

 Europe, there are very few used in this country, and 

 the preponderence of instruments shown in catalogues 

 of foreign makers, would indicate the same tendency. 



Almost all instruments for reliable work are pro- 

 vided with both fine and coarse adjustment. They 

 are both necessary, the only question being whether 

 the latter shall be by the sliding tube or rack and 

 pinion. The former, while perhaps having the advan- 

 tage of admitting a more speedy change of objectives, 

 has a decided disadvantage in the hands of the stu- 

 dents in endangering objectives and preparations. 

 Further than this, it is almost impossible for the 

 maker to center the nose-piece with the tube, so that 

 a change of objectives usually loses an object out of 



