902 Transactions of the American Institute. 



attempts have proved failures. In all these proceedings, directly 

 reflected light proved efiicient. Lately Dr. Vogel tried to make a 

 picture with double reflected light ; the object was a gas machine 

 which stood in a dark corner of the royal academy ; it could not be 

 reached by direct reflected light. He had to use two mirrors, and the 

 rays, after a second reflection, had to be kept longer on the dark parts 

 of the object than on the light ones. The lens was a steinheil aplana- 

 tic, Xo. 3, with the third stop ; time, July 24, between three and 

 four p. M. Pie found that an exposure of from eight to nine minutes 

 was necessary to obtain a good negative. This goes to show how 

 large an amount of actinic force is lost by reflection, as the same lens, 

 wath direct light, w^ould have required an exposure of twenty-tive 

 seconds. In this connection he mentions the extraordinary diflerence 

 in the actinism of sunlight, during difterent seasons of the year. 

 For instance, under the flftieth parallel of northern latitude, the 

 intensity of light on the 21st of December, at noon, is only equal to 

 the intensity at six and a half p. m. on the 21st of July. In this 

 respect the photographers of the southern hemisphere have the advant- 

 age over us, as, with them, Christmas happens in midsummer. 



The Colors of Foliage. 



The London Athenseuni says : " Experiment has confirmed the 

 conclusion of an American scientist that leaves turn red, at the end 

 of the season, through the action of an acid, since one of tlie elements 

 producing the green color must be a vegetable blue. Autumnal 

 leaves placed under a receiver, with the vapor of ammonia, in nearly 

 every instance lost the red color and renewed their green. In some, 

 such as the sassafras, blackberry and maple, the change was ra])id, 

 and could be watched by the eye, while otliers, particularly certain 

 oaks, turned gradually brown without showing any appearance of 

 green." 



Oenoline. 



M. Morat gives in a German journal the process for separating 

 oenoline, the coloring matter met with in genuine rod wines obtained 

 from grapes. It is composed of ten equivalents of carbon, ten of 

 hydrogen, and five of oxygen. Young red M'ines contain, moreover, 

 a pigment solu])le in acetic and batyric ethers, Avith a bluish violet 

 color, becoming green by ammonia, and finally turning brown. Some 

 chemists consider that this material is identical with cyanine; it is 

 not a very stable compound, and is only found in young wines. The 



