59 



of the lateral movement, bring it across again and 

 thus through the entire specimen, or until the 

 object is found or the specimen searched over. 



Nose-Piece.--This being the lower end of the 

 body, to which the objectives are attached, it is 

 important in so far as it must be accurately made. 

 As stated it has the society screw. Previous to 

 1857 each maker followed a standard of his own 

 and this to a great extent is still the case on the 

 Continent. The Royal Microscopical Society of 

 London appreciating the inconvenience of this 

 diversity, recommended a standard thread of 36 to 

 the inch with an external diameter of 0.8 inch, 

 which was finally adopted in England and this 

 country. The Society supplied to the makers a 

 so-called standard hob or tap with which to gauge 

 the thread. Unhappily, however, these taps are 

 not to a standard, as there is a variation in those 

 which are sent out by the Society, so that while the 

 public is under the impression that there are fixed 

 dimensions there is a diversity in the products of 

 different makers, so that it often happens that the 

 objectives of one maker will not enter the stand 

 of others. The writer in 1884 read a paper on this 

 subject before the American Society of Micro- 

 scopists and as a result a committee was appointed 

 to bring about a better state of affairs. It failed, 

 however, in obtaining the co-operation of the 

 Royal Microscopical Society, the main reason 



