MECHANICS AND USEFUL ARTS. 93 



had previously borne the test-pressure ; while the gutta percha pipe, 

 which under the test had not been able to sustain a continued strain 

 of more than 180 Ibs., bore without rupture the same shock. This is 

 owing directly to its elasticity ; the shock was but momentary, and 

 the material yielded sufficiently for its protection. Its toughness and 

 cohesiveness, when properly worked, proved, under various tests, to 

 which it was subjected, to be wonderful. Of its great durability 

 while used in this manner, chemists who have examined the pipe 

 which has been taken up, speak most favorably and confidently. 



The gutta percha pipe used was three inches in diameter the 

 material being | inch thick, and made in lengths of nine feet. The 

 ioints were made as follows : the end of one length was pointed off and 

 partially roughened on its surface with a hot raspq the end of another 

 piece was made flexible by being heated in hot water, then opened by 

 the hand sufficiently, and carefully dried. The pointed end being 

 inserted, and the other closed around it by the pressure of the hand 

 merely, and being suffered to get cool, the junction became perfect, 

 and the whole pipe essentially one piece. Appleton's Mechanic's Mag. 



EXTINCTION OF FIRES IN COAL MINES. 



IN 1849, a successful attempt was made in England to extinguish a 

 fire which had been raging for considerable time in the Astley coal 

 mines,* by means of carbonic acid gas. During the past year another 

 gigantic experiment has been made, by Mr. Gurney, (the gentleman 

 who operated in the former case,) on a coal mine, long known as the 

 " Burning waste of Clackmannan." This fire had raged for about 30 

 years, over an area of 26 acres, in a nine-foot seam of coal. It is sup- 

 posed to have been set fire to by some persons who had been distilling 

 illicit whiskey in it. Shortly after its discovery it rapidly extended 

 itself, and threatened the destruction of the entire coal-field. A sum 

 of 16,000 was laid out in surrounding the fire with a puddle-wall, to 

 prevent its extending to other workings. The wall took five years in 

 building, the workmen being frequently driven back, and obliged to 

 recommence at a greater distance from the fire. It was, however, 

 finally completed 19 years ago. In the building of this wall the lives 

 of nine men and three women were unfortunately lost at various times 

 by the roof falling down and cutting off their retreat, and the fire over- 

 whelming them before they could be excavated. One unfortunate girl 

 was enclosed in this manner, and not burnt, but roasted to death, so 

 that, to use the expression of those who found her, when they took hold 

 of her arm to lift her it came off like the wing of a roasted fowl. The 

 fire having taken place near the crop of the coal, it was surrounded by 

 running the wall from the crop in a form resembling nearly a semi- 

 circle towards the dip, and then round again towards the crop, so that 

 the line of the crop formed the diameter of the circle. Still, however, 

 the wall required constant attention ; as, if the fire once passed it, it 

 would be a matter of great difficulty and expense again to surround it. 

 In consequence, it has cost the owner of the property (the Earl of Mans- 



* See Annual of Scientific Discovery for 1850, pp. 191-5-6. 



