Absorption by the Humors of the Eye.--SI. de Chardonna finds that most of the rays ef the solar spectrum traverse the cornea and the vitreous humor, but the spectrum of the crystalline lens corresponds exactly to the visible spectrum, and he thinks that lens has the physiological function of intercepting all the ultra-violet rays. He was, therefore, led to inquire whether our failure to see those rays is owing to an insensibili V of the retina or to the fact that the raysd0 not reach it. Dr.

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... llard thrnished him with two subjects, who had had the crystalline lens removed in eperations for cataract. The retina, in both eases~ was as sensitive to the ultra-violet rays as to the visible rays. --Comptes Ren(h~s, Feb. 19, 1883. C. Age of Vegetables.--It is generally thought that the age of trees m'ty be ascertained by the number of concentric ligneous layers, each layer corresponding to the growth of a year. This principle is not applicable to tropleal and equatorial trees, as is shown by the following fi~ct. M. Chareneey visited the ruins of Palenque, in Mexico, in 1859 and in 1881. On one occasion he cut off the branch of a shrub, which he judged by its size to be about eighteen months old, but he tbund eighteen concentric layers. On his first expedition his party cut down several trees~ in order to get at the pyramid. New shoots have since grown, which must, of course, all be of the same age, twenty-two years. On one of them M. Chare,mey counted 230 concentric layers.--Les Mondes, Feb. 10, 1883. Modifications of Glass at Moderate Temperatures,-Messieurs Crafts and Pernet have presented some recent communi('ations to the French A_oademy, relatively to the changes which thermometers undergo when they are heated for a long time. In manufactories of printers' ink, where oils are heated to a temperature of 2700 (538°F.) i~)r many days, the most ace.rate,thermometers often become so (;hanged as to indicate errors of ten or more degrees. J. Saller0n cal% attention to similar' changes at much lower temperatures. The areometers which are employed in sugar refineries where molasses is treated by osmosis, are phmged for many clays in liquids which m' e heated to 95 ° (203°F.). Although this temperature is t)elow the b0iling point of water, it is sufiqcient to completely modiI~ the areomete~s and to soften the glass enough to make them untrustworthy.--Comptes Rendus. C.