TROCEEDTNGS OP THE POLYTECHNIC ASSOCIATION. 311 



They found that fruit passed through three stages. In the first stage the 

 fruit is green, and behaves to the atmosphere like a leaf, in decomposing 

 carbonic acid and giving oil oxygen In the second stage, that of ripen- 

 ing, tin's action is reversed — oxygen is absorbed and carbonic acid exhaled 

 from tiie cellules of the pericarp, in consequence of a series of slow com- 

 bustion, in which the immediate soluble principles disappear. Taunin goes 

 first, then acids, and afterwards sugar. In the third stage, that of decom- 

 position, the effect of which is the liberation of the seed, air enters the 

 cellules, sets up alcoholic fermentation, and the acids of the fruit give birth 

 to true ethers. Finally, it not only decomposes the cellules, but oxidizes 

 certain constituents which have resisted the changes in ripening ; thus 

 certain fruits, like the medlar, very acid and astringent, only become eata- 

 ble when they arc mellow. 



Condensation on the Surface of all Solids. 



Prof. Magnus describes in Peggendorf's Annalen a series of delicate 

 experiments made by him, from which he concludes that all substances, 

 however different they may be, are raised in temperature when air comes 

 in contact with them which is moister than that surrounding them; and 

 that they are depressed in temperature when they are exposed to air which 

 is drier than that by which they are surrounded. The most various vapors 

 condense on the surface of solid bodies in such quantity as to cause an 

 appreciable elevation of temperature ; and from this it follows that at all 

 times there is at the surface of bodies a laj^er of condensed vapor, which 

 is larger or smaller according to the hygrometric state of the atmosphere. 



A Bridge over the Straits of Messina. 



The Italian journals announce that it is in contemplation to unite Sicily 

 with Italy by a bridge, to be constructed on a new S3^stem. The chains 

 will be made of cast steel, and strong enough to support the weight of 

 several railwa}'- trains. 



New Maritime Sounding Apparatus. 



M. Gouezel has invented an apparatus in which the suspension line is 

 dispensed with. It consists of a rod of iron, furnished with nippers at the 

 extremity, which supports cylindrical weight capable of being detached 

 from the rod; above the weight a float of hollow metal is fixed, which con- 

 tains a small clock so arranged as to stop by concussion ; a bell is also 

 attached, and above the whole a signal. The time of dropping the appa- 

 ratus is noted; on striking the bottom the clock is stopped, and the float is 

 detached and rises to the surface; the depth, is calculated from the time of 

 the descent. The objection to long lines in deep-sea-soundings, which are 

 bent by under-currents, seems to be obviated by this invention. 



Silk-Worms. 



M. Oncsti has found that wood-soot, if sprinkled over diseased silk- 

 worms, effects an almost certain cuie, or at all events prolongs their lives 

 until the cocoons are finished. The Minister of Agriculture of France has 



