( 178 ) 

 PROCEEDINGS OF THE SOCIETY. 



Meeting of Sth December, 1886, at King's College, Strand, W.C, the 

 President (the Rev. Dr. Dallinger, F.R.S.) in the Chair. 



The Minutes of tlie meeting of lOtli November last were read and 

 confirmed, and were signed by the President. 



The List of Donations (exclusive of exchanges and reprints) received 

 since the last meeting was submitted, and the thanks of the Society given 

 to the donors. 



Lee, A. B., autl F. Hennoguy, Traite des Methodes Teclmiques de From 

 I'AnatoiDie Microsoupiqiie, Histologie, Embryologie and Zoo- 

 logie. Avec une preface de M. Eanvier. ix. aud 488 pp. 



(8vo, Paris (1887) 1886) Mr. A. B. Lee. 



Microscopical Eecords. (4to, Rochester, N.Y., 1886) Mr. C. E. Ailing. 



Electric (Incandescence) Lamp for the Microscope Mr.R. P. Hart Durkee. 



Seven Slides and li Specimens of American Fresh-water Sponges Mr. B. W. Thomas. 



Mr. Crisp read a letter received from Mr. Durkee, the designer of the 

 electric lamp which was described and figured in the December number of 

 the Journal (p. 10 J3), and there stated to have been " received anonymously 

 from America." The letter explained that a full descrijition had been sent 

 by the same mail as the lamp, but it had miscarried, and the letter now to 

 hand vmfortunately did not arrive in time for the explanation to be inserted 

 in the Journal with the description. 



Mr. J. Mayall, jnn., said that Mr. Crisp at their last meeting had 

 pointed out that if Microscopes were to be made for every special purpose 

 for which they could be used, there would be a large field open, and he 

 had to introduce to their notice that evening another of this class. It had 

 been designed to measure with great accuracy the divisions ruled upon 

 diffraction-plates, which was about the severest test that could be applied to 

 any method of dividing fine lines. The Microscope uj)ou the table had been 

 constructed with great care by Mr. Hilger after the designs of Sir Archibald 

 Campbell, and was capable of executing measurements over a space of nearly 

 6 in. Tbe diffraction-plates with which they had hitherto been familiar 

 only occupied a space of about 1 in. ; but he believed Sir Archibald had 

 devised a ruling machine which would be able to rule to 6 in. Mr. Mayall 

 then described the instrument. 



Mr. Mayall also exhibited and described a new form of heliostat, also 

 made by Mr. Hilger, for use in solar photo-micrography, consisting of a 

 plane mirror equatorially mounted and rotated by a clockwork movement, 

 but also having a second mirror mounted upon a universal joint attached 

 to the polar axis, so as to admit of motion in any direction. The pencil of 

 sunlight reflected from the first mirror could, by means of the second, be 

 directed in any desired direction, affording to the worker the very great 

 advantage of being able to place his Microscope and camera in any position 

 he pleased. When properly adjusted, with the jiolar axis parallel to that 

 of the earth, the clockwork would enable the reflected beam to preserve 

 the same direction for about six hours. 



