522 Transactions of the American Institute. 



TIN FOILu 



Nearly all tin foil uow used is adulterated by lead. Dr. J. H. 

 Btddock found, by chemical analysis, that common tin foil contained 

 86.96 per cent of lead; embossed foil, 76.57 per cent; tea foil, 

 SSM per cent, and the so-called pure tin foil, 32.62 per cent of 

 lead. The adulterated article is made by placing an ingot of lead 

 between two ingots of tin, and rolling them into sheets which havo 

 a eoatinor of tin on both sides. * 



COLD AFFECTING THE REGULAR GROAVTH OF TREES. 



At the late Botanical Congress, Prof. Caspary, of Konigsberg, 

 gave the results of some elaborate observations on the effect of 

 low temperatures in altering the direction of the branches of trees. 

 He stated that different species were acted on in diverse ways; 

 some species move, during a frost, directly upward, while others 

 move downward; but in nearly all there was a lateral movement 

 toward the left. 



Vrr^VLITY OF SEEDS. 



M. Pouchet, of Rouen, had found that a small proportion of the 

 seeds of Medicago Amenccaia, a leguminous plant, can withstand a 

 continuous boiling four hours, without losing their vitality. Many 

 seeds thus treated were broken open, their outer integument not 

 beiuo- able to resist the swelling of the contents; but those seeds 

 which resisted the high temperature, retained their power of germi- 

 nation, and sprang up in the course of ten or twelve days after they 

 were sown. 



GILDING BY ^ViHIALGAMATION. 



M. Dufresne, of Paris, has introduced a new process for gilding. 

 He first covers the article to be gilded, by decomposing a basic 

 salt of mercurj' , by means of a galvanic battery, then precipitates 

 o-old by the same means upon it; and lastly, covers the article with 

 another deposit of mercury. The article is then heated in a fur- 

 nace until the mercury passes off as a vapor, when the coating of 

 gold is found adhering to every part of the surface. If the voli- 

 tilization of the mercury is carried on in a close furnace, there will 

 be no danger to the workmen. 



NEW USES OF mCA. 



Mica, coated with a silver film, is now used in this country for 

 large reflectors. Puscher, of Nuremberg, has suggested the employ- 

 ment of silvered mica for covering cuiTcd surfaces, the flexibility 



