“The order of charging and firing is as follows: When the drill holes have been completed, (say every four hours) signal is made, for the cartridges which are only then taken into the Tunnel, (the Nitro-Glycerin in its containing cartridge in one vessel, the exploders, with priming and connecting wires attached, in another separate vessel.) On arrival at the heading, the miners are dismissed to a safe distance, the drill holes are then gauged, to be assured they will receive the cartridges; now, and for the first time the exploders are attached to the Nitro-Glycerin cartridges, and immediately passed into the drill holes, these latter are plugged with a bung, perforated to allow the delicate connecting wires to pass, (thus avoiding cutting the insulation against the rock, and confining the flame;) connection is made beginning with the return wire to the cartridges consecutively, and on to the conducting wire. The operator now retires from the heading some 300 feet towards the shaft where a simple but important apparatus, or break is arranged; he then and there connects his return wire and his conducting wire to two similar wires that lead to the electrical discharge, which duty is performed in the dry, warm room before referred to, and the explosions take place instantaneously. The above modification is a necessity to avoid the damaging influence of the moisture in the Tunnel, so disturbing in its effect on the machine. I have only to add, that we have under-way apparatus for coating and re-covering damaged insulated wires, an improvement to insure perfect explosion of the Nitro-Glycerin; the manufacture of Abel’s priming for fuse, the formula having been published by the inventor; matters of comparatively minor importance, but where so many blasts are daily occurring, involving considerable saving in cost and express charges, and securing a better article when made by the individual for his own actual use, than when made simply for sale, all tending to greater safety and certainty in firing the blasts, ameliorations that have already been submitted to and approved by your engineer in charge, who will doubtless speedily report the actual results of blasting operations. Respectfully, GEO. M. MOWBRAY, Operative Chemist. The following letter from the Engineer in charge to the Commissioners, is interesting, as showing that the Nitro-Glycerin we had made, was superior, and possessed far more valuable properties, than that which had been imported from Hamburg: NORTH ADAMS, FEB. 18, 1868. To the Commissioners of the Troy and Greenfield Railroad and Hoosac Tunnel