would have been much cheaper to use in this case. Gunpowder does not blast to the depth of the holes drilled, whilst Nitro-Glycerin tears the rock from the bottom, and here seems to have penetrated three feet beyond. The reason it was not used before, was the difficulty in procuring it. The nearest factory was that of Mr. Mowbray at Titusville, and the local as well as state laws were such that it could not be transported, except by private conveyance, which added to its cost. That used was carried to Corry in Mr. Mowbray’s carriage, over a very rough road, and thence by special train to this place. If pure, the danger in the use of Nitro-Glycerin is no greater than that of powder, and the premature explosions that have proved so fatal in many instances, have without doubt been caused by decomposition, which was the result of imperfect manufacture. If regularly manufactured, accidents will be the result only of inexperience or the neglect of instructions from those having experience. In the manufacture, the nitrous vapours that are disengaged at the time of mixing, if not entirely expelled, will make it liable to explosion from any concussion, and from Mr. Mowbray’s experience in a number of instances with that manufactured by himself, I should judge his Nitro-Glycerin to be as safe as powder in the hands of experienced persons. It is of a light yellowish color, with pungent aromatic taste, rather sweet than otherwise, and is so poisonous, that in handling, should one allow it to remain on his hands, it would produce intense head ache. It does not explode from the application of flame to its surface, yet will burn, but explodes only from severe concussion, as by the explosion of detonating mixtures and fulminates. I write to you hoping you will communicate any information my letter may contain to General Newton, as it may serve Mr. Mowbray, who I think has made a great improvement in the manufacture of Nitro-Glycerin, and as he gives it his personal attention, I have no doubt it is superior to any now used. I was much pleased to receive the report of the blasting in California, and should interesting professional papers be published by the Bureau, let me beg you will remember Your sincere friend, G. CLINTON GARDINER. The experiments above narrated and conducted under the supervision of Major Gardiner, were continued, (on the removal of the Major to the Pennsylvania Central’s works at Altoona,) by F. J. Wilson, under General Superintendent Wm. A. Baldwin, and the results expected were entirely fulfilled, as will be seen by the subjoined communications: SUBMARINE BLASTING WITH NITRO-GLYCERIN; RESULTS AS COMPARED WITH BLASTING POWDER, IN ERIE HARBOR, MAY, 1870.