PROCEEDINGS OF THE SOCIETY. 651 



The Professor explained and illustrated by diagrams on the black- 

 board the essential points of the views he put forward in 1874, as to the 

 manner in which the microscopic image is formed, and the causes of the 

 appearance presented by certain details in the image, which he showed 

 to be due to the influence of the internal structural constitution of tlie 

 object upon the rays of light transmitted through it, the microscopic 

 image of an object with very fine details being in fact composed of two 

 images, an " absorption image " and a " diffraction image," and the 

 ordinary theory that explained the formation of the image by the 

 geometrical method, and attributed the action of wirl<^-angled glasses 

 to shadow effects, being altogether fallacious. He showed the produc- 

 tion of spurious lines, hexagons, &c., in the same object, when different 

 diajihragms were used, and gave other interesting demonstrations of 

 his theory, with a perfection (by means of the new apparatus) that 

 could not be attained with the ordinary Microscope. 



The Professor's views have already been published in extenso,* but 

 he added a new demonstration, of which he has promised to write a 

 short explanation for the October number of the Journal. 



Scientific Evening. 

 The second Scientific Evening of the Session was held in the 

 Libraries of King's College, on the evening of Wednesday the 21st 

 May, 1879. 



The following were the objects, &c., exhibited : — 

 Dr. E. W. Alabone : 



Dissection of drone-fly, showing sucking stomach, chyle stomach, 

 tracheal vessels, nervous system, &c. 

 Mr. P. W. Andrews : 



Crystals from the surface of an ancient terra-cotta Etruscan vase, 

 and from a glazed terra-cotta Spanish mosaic of the fifteenth 

 century. 

 Mr. Charles Baker : 



Model binocular and model histological Microscopes. 

 Mr. W. A. Bevington : 



Stephenson's erecting Microscope, 

 Lung of frog. 

 Mr. Arthur Cole : 



A series of 24 slides of aromatic salts for the polariscope, prepared 

 by Dr. Otto N. Witt. 

 Mr. Frank Crisp : 



Melicerta tubicolaria. 

 Trachelius ovum. 



* See ' Arch. Mikr. Anat.' (Max Schulze), ix. (1874). " Contributioa to 

 the Theory of the Microscope," translated by Dr. H. E. Fripp in the 'Proceedings 

 of the Bristol Naturalists' Society,' n. s., i. (1875) p. 200, and extracted in part 

 in 'M. M. J.,' xiv. (1875) pp. 191 and 245. See also Mr. J. W. Stephenson's 

 paper, " Observations on Prof. Abbe's Experiments illustrating his Theory of 

 Microscopic Vision," in ' M. M. J.,' xvii. (1877) p. 82 (1 plate), and Mr. Crisp's 

 "On the Influence of Diffraction in Microscopic Vision," ' Journ. Quek. Micr. 

 Club.,' V. (1878) p. 79 (1 plate). 



