136 



observations from any gentleman present npon the subject, though he 

 thought they must admit that it was very difficult to come after Dr. Cooke, 

 seeing that what he said was usually almost exhaustive. Meeting with 

 no response, he then called upon Mr. Ingpen to give them some observations 

 upon a question of great optical importance ; he need not tell them that 

 much depended on how they saw things, the importance of the question 

 often depending far more on hoiv than ivhat they saw. 



Mr. Ingpen then gave an account of the present state of the " angular 

 aperture" question, and exhibited and described Professor Abbe's 

 Apertometer. 



The Chairman invited observations upon the very interesting subject 

 which had been placed before them, and thought that Mr. Ingpen had 

 thrown a flood of light upon a matter which was a very difficult one. The 

 presence of oil between the front lens and the object stood much in the 

 same relation as the field lens of the eye-piece to the eye-lens ; it collected 

 rays which would otherwise be lost. If the field glass of an eye.piece was 

 taken out, they would still see the object, but only a small portion of it, 

 though more magnified, but when placed in its position again they would 

 find that the field lens gathered in many rays of light which would other- 

 wise be lost. He might compare this effect to that of a number of wires 

 surrounding a hyacinth in its glass ; they spread out very much until a ring 

 was put round them to gather them together. 



Mr. Ingpen further illustrated this effect by a drawing on the blackboard. 



The thanks of the meeting were unanimously voted to Dr. Cooke and Mr. 

 Ingpen for their communications. 



Announcements of meetings for the ensuing month were then made, and 



the proceedings terminated with a conversazione, at which the following 



objects were exhibited : — 



Stained tissue of Cystsopteris bulbife?'um ... ... Mr. T. H. Buffham. 



Lining of nest of English Trap-door Spider — Atypus^ 



„ , . ( Mr. F. Enock. 



Sulzeri ... ... ••• ... ... ••• t 



Section of leaf of Pinus sylvestris Mr. W. H. Gilburt. 



Pollen of Japanese Lily Mr. W. Goodwin. 



Various Anatomical Injections ... ... ... ... Mr. J. J. Hunter. 



Attendance — Members, 44 ; Visitors, 5. 



September 13th, 1878. — Conversational Meeting. 



The following objects were exhibited : — 



Cuticle of Water-cress, showing crystals and raphides Mr. F. W. Andrew. 



Elytron of Oak Weevil Mr. G. Beaman. 



Dentate Antennae of Goat Moth Mr. F. Enock. 



Frond of Stag-horn Fern, transverse section, double^ ^ ^ ^ Gnburt 



stained ... ••• ••• ••• ••• ••• ) 



Hairs of Deutzia scabra Mr. W. Goodwin. 



Section of Jaw of Cat, showing four teeth Mr. J. J. Hunter. 



