104 ROYAL MICROSCOPICAL SOCIETY STANDARDS [Ch. Ill 



is a reasonable certainty that the universal screw for microscopic 

 objectives may be realized. It is astonishing to see how widely the 

 " Society Screw " has been adopted. Indeed there is not a maker 

 of first-class microscopes in the world who does not supply the objec- 

 tives and stands with the " Society Screw," and an objective in Eng- 

 land or America which does not have this screw should be looked upon 

 with suspicion. That is, it is either old, cheap, or not the product 

 of one of the great opticians. For the Standard, or " Society Screw," 

 see: Trans. Roy. Micr. Soc, 1857, pp. 39-41; 1859, pp. 92-97; i860, 

 pp. 103-104. (All to be found in Quar. Jour. Micr. Sci., o. s., 

 vols. VI, VII, VIII). Proc. Amer. Micr. Soc, 1884, p. 274; 1886, 

 p. 199; 1893, p. 38. Journal of the Royal Microscopical Society, 

 August, 1896. 



In this last paper of four pages the matter is very carefully 

 gone over and full specifications of the new screw given. It con- 

 forms almost exactly with the original standard adopted by the 

 society, but means have been devised by which it may be kept 

 standard. 



The following discussion and specifications are from the Journal 

 of the Royal Microscopical Society, 1915, pp. 230-231. 



"Objective Screw Thread 



" The question of standardization of the Objective Screw Thread 

 was first discussed by the Microscopical Society in 1857, and the first 

 sizing tools were issued in 1858. 



" In 1896 the Council of the Royal Microscopical Society issued 

 another Report, and drew up a specification defining the limits of 

 variation allowable from the original standard screw thread. 



" Difficulties having arisen in connexion with the testing and ad- 

 justing of the sizing tools supplied by the Society, the Council in 191 1 

 appointed a Gauges Committee to look into the question of obtain- 

 ing and testing further tools, and they now have pleasure in informing 

 Fellows of the Society that an arrangement has been made with the 

 Director of the National Physical Laboratory whereby the standard 

 gauges of the Society have been deposited at the National Physical 

 Laboratory. The Council has also arranged for the issue of new 



