PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 919 



the difference in the action of these bodies is that masfnesia is a 

 weaker base, and parts with the chlorine more easily than lime. 



Solvent for Fibers. 



A solution of copper in ammonia is said to be a solvent for veg- 

 etable as well as animal fibers, such as wool and silk. It is capa- 

 ble of so penetrating one kind of fiber with a solution of another 

 as to unite certain of their qualities; for example, enabling cotton 

 to receive and retain the same dies with woolen, and with a similar 

 tendency. 



Astrolabe. 



A very curious instrument for taking the altitude of the sun 

 or stars at sea, made by the celebrated Arabian astronomer and . 

 mathematical engineer, Al)dul-Aima, has l)een presented by the 

 Minister of Puljlic Instruction in Persia to M. Duruy, Avho has 

 placed it among the collection of instruments in the Paris Observ- 

 atory. 



Berlin Ware. 



According to Dingler's Polytechnic Journal this ware, highly 

 valued by chemists, is composed of forty-five parts kaolin (a sill, 

 cate of alumina), 37^ parts pure alumina, and 16^ parts felspar (a 

 mixture of silica, alumina, and either potash or potash and soda). 

 The enamel is composed of forty-two parts sand, thirty-three kaolin, 

 thirteen unburned gypsum, and twelve of the baked composition 

 first described. 



Mountain Attraction. 



The pendulum experiments now carried on in India in connec- 

 tion with the trigonometrical survey, under Lieut.-Col. Walker, 

 have led to new ipid important conclusions regarding mountain 

 attraction. Theoretically the force of gravity should be greater 

 as the observing station approaches the Himalayas, but the reverse 

 is found to be the fact. Col. Walker, in a communication to the 

 Royal Society of London, says this seems a remarkable confirma- 

 tion of the Astronomer Eoyal's opinion, that the strata of earth 

 below mountains are "less dense than the strata below plains and 

 the bed of the sea. 



Artificial Manure. 



The manure made by M. Ville, and applied to the model farm 

 of Napoleon near Vincennes, has the following* composition and 

 cost : 



