910 Transactions of the American Institute. 



A good test is to try the leaves after they have been gently boiling 

 for an hour, and if the cellular matter does not easily rub off betwixt 

 the finger and thumb beneath cold water, boil them again for a short 

 time. When the fleshy matter is found to be sufficiently softened, 

 rub them separately but very gently beneath cold water until the per- 

 fect skeleton is exposed. The skeletons, at first, are of a dirty-white 

 color; to make them of a pure white, and therefore more beautiful, 

 all that is necessary is to bleach them in a weak solution of chloride 

 of lime, a large teaspoonf nl of chloride of lime to a quart of water ; 

 if a few drops of vinegar is added to the solution, it is all the better, 

 for then the free chlorine is liberated. Do not allow them to remain 

 too long in the bleaching liquor; or they become too brittle, and can- 

 not afterward be handled without injury. About fifteen minutes will 

 be sufficient to make them white and clean-looking. Dry the speci- 

 mens in white blotting paper, beneath a gentle pressure. Simple 

 leaves are the best for young beginners to experiment upon ; the vine, 

 poplar, beech and ivy leaves make excellent skeletons. Care must be 

 exercised in the selection of leaves, as well as the period of the year 

 and the state of the atmosphere when the specimens are collected ; 

 otherwise, failure will be the result. The best months to gather the 

 specimens are July and August. Never collect specimens in damp 

 weather, and none but perfectly matured leaves ought to be selected. 

 The President then introduced Dr. Henry Morton, who read the 

 following paper: 



On Certain Phenomena of Fluorescence. 



By Henry Morton, Ph. D., President of the Stevens' Institute of Technology, 



Hoboken, N. J. 



Though Sir John Herschel and Sir David Brewster, as well as 

 others, had noticed some actions now known as fluorescent, it is to 

 Prof. Stokes that we owe the first thorough study of the subject, and 

 the true explanation of the action involved; and though much labor 

 has been since expended in the same direction, by Becquerel, Glad- 

 stone, Hagenback, and others of less note, little has been done beyond 

 adding to the store of facts which may, perhaps, enable some future 

 philosopher to throw light upon the recondite methods of actions, 

 whose general result alone we are able, as yet, to recognize. 



This general relation of cause and effect is, however, a very inte- 

 resting one, and with its illustration I will ask you to occupy your 

 selves this evening. 



In order that my relation should be connected and consecutive, I 



