1084 Transactions of the American Institute. 



The photograpliic lenses from one Paris firm have for a long time 

 been celebrated for the rapidity of their action, which seems to result 

 from color alone. When carefully examined, they present no novel 

 feature of configuration or extraordinary amount of polish. In the 

 flint portion of their lenses, no color can be detected, while the 

 crown shows a delicate pale blue tinge, instead of the green or yellow 

 80 often seen upon a close inspection of many lenses. 



By any one who has experimented (photographically) with decom- 

 posed light, the efiect of this color in a lens will at once be understood. 

 It is believed that all the obstacles thus far presented, may be sur- 

 mounted, and a cheap, efi'ective, easily managed artificial light 

 produced, suitable for many of the constant requirements of photo- 

 graphers ; and, to meet these conditions, no means now seems more 

 pronaising than that offered by compressed hydrogen and oxygen 

 gases, united in proper proportion at or near the point of ignition, 

 and the flame thus produced directed upon a pencil of the oxyd of 

 one or more of the metals before named. For. some purposes, it 

 would doubtless be advantageous to impart to the light a tint of blue 

 or violet, by the admixture of some color-producing property in the 

 pencil upon which the flame impinged, while, in the selection of our 

 condensing lenses and objectives, especial attention should be given to 

 color in the glass ; and all lenses for photographic purposes should 

 be protected from solar light, even if diffused, at all times when not 

 in actual use. 



M. Boutemps (managing director of one of the celebrated crystal 

 glass works of France), after a long and careful study of the subject, 

 attributes the change to the oxydizing effects of the sun's rays upon 

 the metals used in manufacturing the glass. 



Mr. Chapman made remarks upon the great necessity for a good 

 artificial light, especially in large towns and cities. 



Mr. Anthony described some experiments which he made some 

 years ago, in the production of very sensitive collodion phites. He 

 had succeeded in producing plates so extremel}'" sensitive that he was 

 obliged to m.anipulate in perfect darkness ; the faintest ray of arti- 

 ficial light produced a foggy image. He had not succeeded in 

 making the process practical, but might renew the investigation. 



The Section then adjourned to the first Tuesday in April. 



