The Microscope. 149 



it was seriously thought of in Europe.' The swinging tail 

 piece, first definitely adopted by an American maker, is rapidly 

 becoming an essential feature of every good stand, and the Zent- 

 mayer slip stage, for those who desiife a slip carrier, is univers- 

 ally acknowledged to be the best made. Let any competent 

 student take an American type of student stand in a laboratory 

 supplied with the clumsy and inconvenient German stands 

 usually furnished to students, and he will immediately become 

 envied by his associates because he possesses an instrument bet- 

 ter adapted for all kinds of work than those the others have. 



In conclusion there is one point on which we may make an 

 improvement. 



In 1884 the American Society of Microscopists appointed a 

 committee to see if some arrangement could not be effected with 

 the London Society to improve the character of the taps for the 

 universal screw sent out by the London Society. In 1887 that 

 committee asked to be discharged, on the ground that the cor- 

 respondence which had taken place showed that it was imprac- 

 ticable to make any arrangement with the London society. Now 

 it is a pertinent question if we are obliged to be content with the 

 present unsatisfactory state of this matter. The number of mi- 

 •croscopes now made in this country is very large and is increas- 

 ing. Unless steps are taken to secure taps of standard guage and 

 size, no uniformity will ever be attained. 



One of the principal difficulties in the way is understood to 

 be that the shape of the thread unfortunately chosen is not adap- 

 ted for grinding true. Now as the effort for cooperation has 

 failed, it might be better to start independently, and make our 

 •own standard taps, since we have both the skill and the appar- 

 atus to do it better than it is done in Europe, and if we agreed 

 among ourselves, there is little doubt but that our standards 

 would be accepted. 



The indictment brought against those furnished by the Lon- 

 don Society is that they were not round, that they were unlike 

 in size and pitch. It may be that if a cylindric head with bayonet 

 catch had been adopted in place of a screw, it would have been 

 easier to make an accurate fitting, as it is a difficult matter to 

 turn or cut a screw thread that shall collimate precisely. Be 



3. Zeitschrift f ur Instrumenten Kunde, 1890. pp. 1-6, trans, in Queen's Bulletin, 

 Feb. 1891. 



