422 ANNUAL KECORD OF SCIENCE AND INDUSTRY. 



in a cupola furnace, and allowed to cool for the same length 

 of time. 



The stone shows in its fracture coarse, irregular, grayish- 

 white fragments of quartz, inclosed by a light brownish-yel- 

 low finer mass, and swells in the fire instead of contracting. 

 Metallic oxides and strongly basic slags attack this quartz 

 rock very rapidly ; and, like quartz, it will not stand rapid 

 changes of temperature. In storing away this material it is 

 to be protected from wet. 



Dr. Carl Bischof, of Wiesbaden, who has lately published 

 an investigation into the nature and theory of the formation 

 of this stone, remarks that for a rational and suitable manu- 

 facture there are three requirements: First, that the rock must 

 be as pure as possible, and in its essential features be of about 

 equal fusibility with pure quartz; second, that the baked 

 stone should possess and maintain sufficient density and con- 

 tinuity, since if otherwise, even with greater infusibility, the 

 germ would be implanted of destructibility in the fire ; third, 

 that the air-dried stone should already have enough compact- 

 ness to be susceptible of handling almost as readily as if 

 burned. 14 C\ CCL, 339. 



DRILLING TRIANGULAR HOLES FOR BLASTING. 



A correspondent of the " English Mechanic" states that in 

 the Cleveland district it is now usual, w r hen boring for blast- 

 ing purposes, to make the holes of a triangular section instead 

 of circular, as in the conventional style, and to effect this the 

 boring bar or jumper is partly turned on each side of its cut- 

 ting alternately. No difficulty is experienced in boring the 

 holes to this shape, and they are found more effective than 

 round holes, the corners forming points at which the fracture 

 of the material operated on appears to commence, the line of 

 fracture usually forming a prolongation of the triangle. The 

 holes averaged three feet six inches in depth, and are gener- 

 ally made in thirty or forty minutes. The powder charges 

 vary from one to two pounds, according to circumstances. 

 IS A.August 25,1871,500. 



SHIP CANAL ACROSS CAPE COD. 



Among the numerous engineering projects of the present 

 day, few promise to be of more importance in a commercial 



