622 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



of foraminifera, minute algise and diatoms. Dr. Kelaart Las suggested 

 that the siliceous internal skeletons of these microscopic diatoms may pos- 

 sibly permeate the coats of the mantel, and become nuclei of pearls; ano- 

 ther supposition is, that the ova escape from an overgrown ovarium, and 

 are the origin of the gem. 



A single oyster of five or six years' growth, contains 12,000,000 of eggs. 

 A plan for cultivating the pearl oyster is now being tried by transplanting 

 them as we do the edible oyster. 



Valata. 



This tree, growing in Guiana, yields a juice which is used bj^ the natives 

 instead of milk, in coffee. M. Serres states that this juice is capable of 

 being worked into a product much more flexible than gutta percha, and in 

 every way superior to it. 



The reading of this item brought to the floor Dr. Parmelee, who stated 

 he had eight samples of Valata product, but as yet had only examined its 

 physical properties. It is not softened by immersion in hot water. It can 

 be vulcanized, and seems intermediate between India-rubber and guttar 

 percha. There is no difficulty in obtaining it in large quantities. 



Some gentlemen present having expressed a doubt about its being used 

 in coffee, the Chairman remarked, that Valata juice was evidently a hydro- 

 carbon, and might be digested in its normal state. Gum, starch and cellu- 

 lose, the substance of the vegetable cell, are isomeric compounds, contain- 

 ing an equal number of oxygen and hydrogen atoms, and are sometimes 

 distinguished as carbo-hydrates, yet these three substances differ widely 

 from each other. Gum and starch can be digested, but we are not certain 

 that any animal except the beaver can digest woody fiber. 



Preservation of Animal Matter. 



A method was described before the French Academy by Mons. Pagliari. 

 The substance to be preserved is covered with a mixture of alum and gum 

 bezoine, with water, which forms a layer of varnish over the surface of the 

 substance, thus excluding the air, and completely preventing its decompo- 

 sition. 



A New Lantern Polariscope. 



Mr. Samuel Highley, of London, has invented an instrument to be used 

 in connection with the magic lantern, much cheaper than the gas polari- 

 scopes. To use this instrument the front lenses of the magic lantern are 

 removed, the condensers only being employed, and the source of light re- 

 moved until a beam of parallel rays is produced. The lantern nozzle is 

 then pointed at the " bundle," — consisting of a number of thin glass plates — 

 till the rays are incident to the polarizing angle for glass, the proper adjust- 

 ment of parts being indicated by the appearance of an even disc of light 

 upon the screen. A design is then inserted in the large stage, and its lines 

 of construction focused. The analyzing prism is then placed in front, sus^ 

 tained by an adjustable rod, and the colored eff"ect produced and varied 

 either by the rotation of the prism or the rotation of the design or crystal. 



