PROCEEDIXGS OF THE POLYTECHNIC ASSOCIATION. 941 



a point which was placed above the piece of ijlatinuin, almost, but 

 not fully in contact with it. When a. sound was made in the tube, 

 the vibrations of the diapliragm brought the piece of platinum in 

 contact with the point as many times as there are undulations neces- 

 sary to produce that sound. This instrument was connected with a 

 straight-bar electro-magnet. When the connection with the battery 

 was made the magnet lengthened, and when it was broken the bar 

 returned to its original length. As this took place, for every vibra- 

 tion of the diaphragm there was a corresponding vibration in the 

 sounding-board on which the magnet was placed, giving a tone which 

 corresponded to the one originally sounded. After the examination 

 of this interesting apparatus the meeting adjourned for one week. 



January 14th, 1869. 



Professor S. D. Tillman in the chair; Mr. C. E, Emery, Secretary, 

 The chair presented the following interesting scientific items : 



Dangerous Artificial Saffeo:^. 



A compound used for tinging vermicelli, and made by Mr. Mittens- 

 weg, of Poblitz, has proved to be explosive. The substance ignites 

 as easily as gunpowder. Mr. Chevallier, of the Societe d' Encourage- 

 ment, Paris, has so far not been able, by analysis, to discover its com- 

 position. 



Adultera'i;iok of Tm. 



A report has been published on the quality of the tin coating the 

 cooking vessels used in the French hospitals. The metal used for 

 tinning was found to contain from twenty-five to fifty per cent of lead. 

 In vessels said to be made of pure block tin, the commissioner found 

 fifteen per cent of lead. This amount he believes to be dangerous to 

 the public health, and recommends the government to fix the limit of 

 the amount of lead to be used with tin, in any culinary or drinking 

 vessel, at five or six per cent. 



Alcohol from Lichexs. 



Iceland moss, found in Sweden in large quantities, contains starch 

 and cellulose, which, by means of dilute acid, may be converted into 

 glucose or grape sugar, some specimens yielding as high as seventy- 



