The use of small lead blocks affords another means of determining the rate of detonation or quickness of an explosive. Each block (a cylinder, 2½ in. long and 1½ in. in diameter) is enclosed in a piece of paper so that a shell is formed above the block, in which to place the charge. A small steel disk of the same diameter as the block is first placed in the shell on top of the block, then the charge with a detonator is inserted. The charge is customarily 100 grammes. On detonation of the charge, a deformation of the lead takes place, the amount of which is due to the quickness of the explosive used (Fig. 3, Plate VIII). Sample Record of Tests. The procedure followed in the examination of an explosive is shown by the following outline: 1.--_Physical Examination._ (_a_).--Record of appearance and marks on original package. (_b_).--Dimensions of cartridge. (_c_).--Weight of cartridge, color and specific gravity of powder. 2.--_Chemical Analysis._ (_a_).--Record of moisture, nitro-glycerine, sodium or potassium nitrate, and other chemical constituents, as set forth by the analysis; percentage of ash, hygroscopic coefficient--the amount of water taken up in 24 hours in a saturated atmosphere, at 15° cent., by 5 grammes, as compared with the weight of the explosive. (_b_).--Analysis of products of combustion from 100 grammes, including gaseous products, solids, and water. (_c_).--Composition of gaseous products of combustion, including carbon monoxide and carbon dioxide, hydrogen, nitrogen, etc. (_d_).--Composition of solid products of combustion, subdivided into soluble and insoluble. _3.--A Typical Analysis of Natural Gas._ Used in tests, as follows: Carbon dioxide 0.0 per cent. Heavy hydrocarbons 0.2 ” ” Oxygen 0.1 ” ” Carbon monoxide 0.0 ” ” Methane 82.4 ” ” Ethane 15.3 ” ” Nitrogen 2.0 ” ” ----- 100.00 per cent. _4.--Typical Analysis of Bituminous Coal Dust, 100-Mesh Fine, Used in Tests._ Moisture 1.90 Volatile matter 35.05 Fixed carbon 58.92 Ash 4.13 ------ 100.00 Sulphur 1.04 _5.--An Average Analysis of Detonators._ Used on Trauzl lead blocks, pressure gauge, calorimeter, and small lead blocks: M - l(l/m). Triple-strength exploder. Charge 1.5729 grammes. Mercury Chlorate fulminate. of potash. Specification 89.73 10.27 Used on all other tests: M - 260(l/m). Double-strength exploder. Charge 0.9805 grammes.