272 PEOCEEDINGS OF THE 



convenient or satisfactory as dyed gelatine films cemented between 

 two glasses. For general use it is desirable to have a series of 

 filters which will give, when used either singly or in combination, 

 a successive series of narrow transmission bands through the 

 visible spectrum. The Wratten M series and visual M series 

 fulfil these conditions. For restricted work one or two filters 

 may be all that is necessary. Mr. Pledge then dealt with the 

 various methods of holding filters. The best place is as near the 

 light source as convenient, but it may sometimes be convenient 

 to put the filter over the eye-piece. In conclusion, Mr. Pledge 

 described in detail some of the Wratten filters made by Kodak, 

 Ltd., and showed a series of slides giving a good idea of their use. 

 He also exhibited a large series of the filters themselves. The 

 meeting expressed its appreciation of Mr. Pledge's paper by 

 passing a very hearty vote of thanks. 



Mr. Soar gave an address on " Microscopical Drawing." Mr. 

 Soar said that he could add very little to what Mr. Sufiolk had 

 said to the Club fifty-two years ago. Drawing without auxiliary 

 instruments is only possible to experienced artists, and it always 

 has the disadvantage of affording no clue to the dimensions of the 

 object. Mr. Sufiolk believed that with the aid of a camera 

 lucida or square ruling in the eye-piece anyone could make draw- 

 ings that would be more truthful than those of a more skilful 

 draughtsman made without such aid. In Martin's treatise on 

 the microscope (1742) there is a description of a camera obscura 

 used for drawing, the image being projected on to a sheet of 

 paper in a darkened chamber by the sun's rays. In Henry 

 Baker's book on the microscope (1753) is a description of the 

 employment of a squared micrometer in the eye-piece made of 

 fine wire, the drawing being made on squared paper. Dr. 

 WoUaston's camera lucida was introduced at the beginning of 

 the last century, and since then all sorts of difierent kinds have 

 been made. Mr. Soar finds that the projection method is the 

 least satisfactory, and he uses either the squared micrometer 

 or a camera lucida. Until recently he has used Ashe's, but he 

 is now using an Abbe, which he finds much better than any 

 other he has tried. For thick objects he uses the squared micro- 

 meter with squared paper, tracing the outline on to another 

 piece of paper and finishing freehand. Colour, said Mr. Soar, is 

 of secondary importance, and there is no royal road to its successful 



