96 ANNUAL OF SCIENTIFIC DISCOVERY. 



held in suspension in the air, and floated on with it through the mine. 

 A large portion was in actual solution, but far the greater part was 

 simply mechanically suspended like fine mist, and did not precipitate 

 or condense. When the temperature was sufficiently reduced, as indi- 

 cated by the thermometer, so as to leave no fear of re'ignition, fresh air 

 was blown in by the spray-jet, so as to pass through the mine charged 

 with vapor, in order to cool it enough to allow of its being entered. 

 After a time the jet was reversed, and the air drawn through the mine 

 in a contrary direction, so drawing out the air we had blown in charged 

 with mist ; and we continued drawing out mist or vapor for several 

 days, which showed that it had filled every part of the waste and had 

 remained suspended. The temperature of the air that was drawn out 

 gradually decreased at the rate of about six degrees a day. After 

 about one month's operations the downcast shaft was uncovered and 

 descended, and found to be of a temperature of about 98. A shaft was 

 then sunk into the middle of the burning waste at a point where the fire 

 was supposed to have been the most fierce at the commencement of our 

 operations. The roof was here found to have fallen, so that it was 

 impossible to enter. The fire, however, was extinct. 



CAOUTCHOUC, ITS PROPERTIES AND APPLICATIONS. 



THE following is an abstract of a paper, read before the Royal Insti- 

 tution, London, by Mr. Brockedon, on Caoutchouc, its properties and 

 applications : 



Caoutchouc is a vegetable constituent, the product of several trees. 

 The most prolific in* the substance are, Siphonia Caoutchouc, Urseola 

 elastica,, Ficus elastica, c. Of these, the first-named extends over a 

 vast district in Southern and Central America ; and the caoutchouc 

 obtained from these districts is best adapted to manufactures. The 

 Ficus elastica is abundant over 10,000 square miles in Assam, Asia. 

 The Urseola elastica abounds in the islands of the Indian Archipelago. 

 It is described as a creeper, of a growth so rapid that, in five years, it 

 extends 200 feet, and is from 20 to 30 inches in girth. This tree can, 

 without being injured, yield, by tapping, from 50 to 60 pounds of 

 caoutchouc in one season. A curious contrast is exhibited in the tardy 

 growth of the tree from which the gutta percha is obtained. This tree 

 does not come to its prime in less than from 80 to 120 years. The 

 produce cannot be obtained but by sacrifice of the tree. It is found in 

 a concrete state, between the bark and the wood, after the tree has 

 been cut down ; and it is in this condition that, having been scraped 

 out, it is sent to our markets. When coagulated by evaporation or 

 agitation, caoutchouc separates from the aqueous portion of the sap of 

 the trees which yield it. This solid and fluid cannot afterwards be 

 reunited, any more than butter is capable of mixing with the milk from 

 which it is separated. Some specimens of caoutchouc are harder than 

 gutta percha itself, while others never solidify, but remain in the con- 

 dition of bird-lime or treacle. The process termed vulcanizing was 

 discovered in 1843. A sheet of caoutchouc immersed in melted sul- 

 phur absorbs a portion of it, and, at the same time, it undergoes some 



