THE NEW ACME STAND. 91 



proposes to purchase a stand that he will not feel com- 

 pelled to sell again in a few years, in order to procure 

 a better one ; keep this point well in mind. 



The author, too, unhesitatingly gives his support to 

 those stands having the swing stage and mirror; the 

 advantages accruing from this late improvement are 

 very valuable, of which we make particular mention of 

 one, to wit: 



In former times, when sub-stages were practically a 

 fixture, it became necessary, in order to secure oblique 

 light, to employ acchromatic condensers of wide aper- 

 tures and short focal distance ; the instrument was costly, 

 and necessitated the employment of accurate and expen- 

 sive sub-stage fittings, and, in general, could only be em- 

 ployed at a great sacrifice of pains, time and attention. 

 With the introduction of the swinging sub-stage and 

 mirror, all this is a thing of the past; the wide-angled 

 condenser is no longer necessary for the display of diffi- 

 cult structures; on the other hand, it now seems desir- 

 able to employ condensers of the lowest angles, the 

 required obliquity being obtained by swinging the sub- 

 stage, mirror and condensers to the proper angle. The 

 expensive centring apparatus not being required with 

 the low-angled condenser, their cost and bother are thus 

 avoided; at the same time better results are obtained, 

 and in a simpler and more convenient way. 



There are other advantages, too, pertaining to the 

 use of the swinging stage and mirror, of which mention 

 will be made in the succeeding pages. 



Finally, let me impress on the mind of the reader 



