JOURNAL 



OF THE 



ROYAL MICROSCOPICAL SOCIETY. 



AUGUST, 1907. 



TRANSACTIONS OF THE SOCIETY. 



X, — On the Podura Scale. 

 By Edwaed M. Nelson, 



Plate XVI. 

 (Read April 17, 1907.) 



This is a subject interesting to microscopists only. Almost every 

 other object that can be examined with a Microscope appeals to 

 workers in other branches of science, such as zoologists, biologists, 

 histologists, botanists, geologists, chemists, etc. Even lines ruled 

 upon glass claim some attention from the physicist, but the excla- 

 mation marks on the Podura scale are a veritable Mte noire to 

 every one except a microscopist. 



It is strange, but true, that while the Podura scale has been 

 the most looked-at object of any, it still remains the microscopist's 

 enigma, and this, moreover, in spite of the fact that its structure is 

 by no means so very minute for a microscopical object. 



This year this test becomes an octogenarian, for we learn from 

 Dr. Goring that the Podura test was not known when he read his 



EXPLANATION OF PLATE XVI. 



Fig. 1.— Watered Silk. T. Carpenter. 1827. 



„ 2. — Wedge-shaped Spines. Dr. Goring. 18.30. 



„ 3. — Featherlets. John Quekett. On the Microscope, 1848, pi. 6, fig. 4a. 



,, 4. — Indian Clubs. R. Beck. The Achromatic Microscope, 1865, pi. 7, fig. 1. 



,, 5.— Beads. Dr. Pigott. M.M.J., ii. (1869) pi. 33, fig. e. 



„ 6.— Knobbed Heads. F. H. Wenham. M.M.J., iv. (1870) p. 125. 



„ 7.— Pins. T. F. Smith. J.Il.:\I.S., 1888, p. 499. 



„ 8.— Cuneiform. E. M. Nelson. 1907. 



Aug. 21st, 1907 2 d 



