MECHANICS AND USEFUL ARTS. GO 



being the height of the water at the commencement of the discharge, 

 aud the lower one the height at the close. The pipe on being insert- 

 ed was closed at the end, by clay placed on by hand, which could bo 

 instantly removed on the signal being given ; and instantly restored 

 when the surface of the water in the tank had reached the lower 

 mark. The experiments of discharging through the several tubes 

 were made with great care, and afterward repeated, to verify their 

 accuracy, and the following is the result : 



The same quantity of Avater passed 



Through the straight pipe in 218 seconds. 



Through the one joint pipe in 314 seconds. 



Through the two joint pipe in 371 seconds. 



From this it appears that the increased time required for the flow 

 through the second pipe was over 40 per cent, and for the third 

 pipe over 70 per cent. These experiments decided the question and 

 the proposed plan was abandoned. 



A NEW APPLICATION OF THE SLAKING OF QUICKLIME. 



A novel application of the slaking of quicklime has been proposed 

 by Dr. John Davy, in the Edinburgh New PliilosophicalJoumal, It 

 is well known that as soon as water is added to and absorbed by well- 

 burnt lime fresh from the kiln, an immediate union takes place, the 

 mass becoming broken up and falling into powder, with the produc- 

 tion of much heat and steam. This does not take place when the 

 lijne has been exposed to the action of the air for two or three days, 

 during Avhich the lime generally absorbs a little water. With respect 

 to these phenomena, Dr. Davy records the result of several experi- 

 ments which showed the explosive power of the lime when placed in 

 holes or receivers and treated with water, or with solutions of com- 

 mon salt, carbonate of ammonia, &c. We have no space for the 

 details which led Dr. Davy to suggest the application of the explo- 

 sive force of lime to the blasting of rocks and similar purposes, but 

 give an account of two of his experiments. A boring was made in 

 a block of sandstone about fifteen inches deep and two inches in 

 diameter; this was filled with small pieces of quicklime, and the 

 hole was closed by a plug of wood. No rending ensued, although 

 the hydrate was formed. The elastic expansive force was not supe- 

 rior to the resistance, and the steam was condensed. A second 

 experiment was made, substituting for the boring in a rock a .strong 

 earthenware jar capable of holding about a quart. It was similarly 

 charged, and tightly corked, the cork bound down firmly with a cord. 

 After about 15 minutes an explosion took place, with a report like a 

 pistol. The jar was broken in several pieces, and some of them were 

 projected many yards from the spot. Now as coal is not nearly so 

 resisting as sandstone, and as its boring is easily effected, Dr. Davy 

 expresses the hope that the experiment may be repeated in a colliery. 

 It is easily made, at a cost not worth mentioning, is attended with no 

 serious clanger, and, should it be successful, it may conduce to the 

 saving of many valuable lives. 



