GENTLEMEN:—I have to report that yesterday 4 P. M., we exploded eleven cartridges of Nitro-Glycerin in charges of 1-2 lb. each, in open holes without tamping, with entire success. This experiment was made in the East heading of West Shaft. On approaching the heading, the absence of foul gases and smoke was remarkable, the mass of broken rock lay close to the heading, and there was no appearance of any rock thrown to any distance from the heading. Inquiring of the miners if they experienced any headache, elicited the remark they noticed a pleasant smell, but nothing further. This settles the question of its applicability in a close tunnel. I attribute this freedom from the foul gases which we noticed in our experiments a year since, to the evident purity of this Nitro-Glycerin; it differs greatly from all descriptions of the article, and in appearance from that we imported, being a liquid colorless as water, and free from smell or bubbles. That which we imported was a thick, yellow liquid, quite different in appearance from this. I have requested Mr. Mowbray, who manufactures the Nitro-Glycerin, to take charge of the blasting, and informed him that the Commissioners wish him to assume the responsibility of using the Nitro-Glycerin until further orders, or at least until the system of firing is thoroughly organized among the employees. I enclose his reply, and approve his suggestions, subject to your instructions. I am very truly yours, W. P. GRANGER, Engineer in charge. The Commissioners for the year 1868, report as follows: During the Summer, Glycerin of a very good quality has been manufactured at this point, under the direction of Mr. Mowbray, and has been used for several months in blasting in the tunnel east of the West Shaft. No accident has attended its use. And while its effect in the heading did not meet the expectations of the Commissioners, the result of its operation in the bench below the heading, justifies the belief that with due provision for its economic use, and essential care and attention paid upon its management, it will prove an effective agent in the prosecution of this enterprise. The Superintending Engineer, Benj. D. Frost, Esq., reports as follows: “The following is a statement of monthly progress. Length Total distance driven. from W. Shaft.