296 ANNUAL OF SCIENTIFIC DISCOVERY. 



mond to be ground is brought in contact with the revolving metallic 

 surface. It need hardly be said, that the task of holding a diamond 

 to be ground firmly against the revolving wheel for so long a period 

 of time as is necessary, would be impossible. Continuous pressure is 

 effected in another and very simple manner : the diamonds are 

 imbedded, all except the parts to be ground, in a heavy mass of very 

 fusible solder shaped like a hammer, the handle of which being fixed 

 as to horizontal motion, but free by means of a hinge to move up and 

 down, and the face of the hammer being brought flat upon the side 

 of the horizontal wheel, the operation of grinding, cutting as it is 

 called, proceeds without further trouble. 



ARGENTIFEROUS LEAD MINES OF MIDDLETOWN, CONX. 



ABOUT two miles below the city of Middtetown, Connecticut, on 

 the banks of the Connecticut river, are several excavations, some 18 

 to 30 feet deep, made during the Revolutionary war by a company, 

 for the purpose of procuring lead ore, so as to supply the American 

 troops with lead. It was worked for some time, the ore smelted, and 

 the lead separated from the rock in which it was found imbedded. 

 Not being found sufficiently profitable to make it an object, the work- 

 ing of the mines was discontinued. A recent examination having 

 been made of these old workings, a considerable quantity of silver 

 was found associated with the lead, and the persons interested became 

 satisfied, that it could be worked profitably, and that the quantity of 

 silver would fully pay the whole expenses of working the mines, 

 leaving the large quantity of lead obtained to form the profit of the 

 mining operations. Thus far, although they have worked but a few 

 months, with a small force, and cannot be supposed to have but 

 tested the richness of the veins of silver yet it is paying its way, and 

 even more than that. Lately, some rich veins of silver ore have been 

 discovered and some pure native silver the former being nearly 

 free from the lead mixture. The ore is broken up and then fed to a 

 mill, where it is pounded fine the pounders, of which there are four, 

 being operated by an overshot water wheel, which is carried by water 

 from a dam, with a fall of some 15 or 25 feet. As fast as the ore is 

 pounded sufficiently fine, a stream of water carries it into troughs, 

 where it is washed. From these troughs it is taken out, and sent to 

 New York, where the metals are separated. 



MINERALOGICAL NOTICES. 



The following mineralogical notices have been communicated to 

 Silliman's Journal, July, by Mr. W. T. Blake. 



Apatite. During the past winter a shaft has been sunk upon the 

 vein of crystalline phosphate of lime at Hurdstown, Essex Co., N. Y., 

 and large blocks of massive apatite have been raised ; some of the 

 largest of these masses weighed not less than 200 pounds, and were 

 nearly pure apatite, the specimens have very little color, portions of 



