PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 569 



Willow bark 16 



Sycamore bark 16 



Cloves 13 



Virginia Sumac 10 



Tannin is found in tea and many otiior vegetable products, but tlius far 

 hemlock bark lias been the most economical source for obtaining this arti- 

 cle. The Chairman concluded by saying t^vat several years ago he spoke 

 at length before this Association, on the manufacture of leather in this 

 country. His remarks at that time will be found in the volume of Trans- 

 actions of the American Institute for 1859, from page 527 to page 536 

 inclasive, and for fear of repeating what was then said he would yield the 

 floor to those who would doubtless be able to throv/ new light on the 

 subject. 



Dr. J. W. Richards remarked that man}'- years ago he had some experi- 

 ence in the manufacture of leather, and had learned among other things 

 that pure soft water was essential in obtaining the bark solution. Skins 

 are prepared for use, in the manufacture of leatlier gloves for instance, 

 without being subjected to tannin. The most common tanning process, as 

 it is called, is to submit the skin to the action of alum. Skins may be also 

 cured and prepared by means of oils. Very fine sheep skins are tanned 

 with sumac. Hemlock bark, having considerable resin in it, requires mere 

 time and heat to yield its tannin than oak bark. The sooner tlie tanning 

 liquor is used after being made, the better. It was his opinion that the best 

 leather does not always weigh the most. He once had a pair of shoes 

 made of leather which had the hair of the skin on, and found them imper- 

 meable to water. 



Dr. D. D. Parmelee stated that a great deal of information on this subject 

 could be obtained in Dr. Campbell Morfit's work on tanning. 



On motion adjourned. 



American Institute Polytechnic Association, 1 

 April 6th, 1865. j 



Prof. Samuel D. Tillman, in the chair; B. Garvey, Secretary. 



New Petroleum Lamp. 



Mr. Griswold exhibited his improvement, designed to facilitate tlie per- 

 fect combustion of petroleum in lamps, by bringing into nearer relations 

 the carbon of the oil with" the oxygen of the air. This is effected by means 

 of two plates of mica placed on either side of the wick, which arc designed 

 to keep the oxygen of the air in action for a longer time, and for a greater 

 distance than could be done without them. As the mica is transparent and 

 not easily broken by heat, like glass, its adoption in the manner proposed 

 by Mr. Griswold, is claimed as a decided improvement. 



The Chairman rear! the following interesting summary of scientific news. 



Aniline Black. 



This new derivative from aniline, completes the series of brilliant colors 

 derived from aniline. The mode of production, the way of fixing it on 

 fabrics, and the insensibility to physical and chemical changes which it 



