GEORGE ROBERT GRAHAM CONWAY, M. AM. SOC. C. E. (by letter).--The writer regrets that some features of the works described in this paper have failed to call forth the many useful criticisms which he expected, and his remarks, therefore, are limited to the few points which have been raised. He is particularly indebted to Messrs. Schuyler, Meyer, and Saucedo for adding supplementary information of value to the paper, but regrets that he cannot support Mr. Binckley in his claim that "the entire general design of the system, as well as the extensive hydrological studies and final selection of the sources of water supply, was completed in 1906," etc. On May 1st, 1907, when the writer assumed responsibility as Chief Engineer, he was unfortunately confronted with the fact that very little data and only a few preliminary and incomplete plans were available. His first duty was to report upon the final sources of supply, and the recommendations made in his report (dated July 12th), received Mr. (now Sir William) Mackenzie's approval during the same month. The final plans, upon which the approval of the State Government was definitely obtained, were prepared by the writer during the summer of 1907, were submitted to the Governor of the State, Gen. Bernard Reyes, on October 19th, and received his approval on December 12th, 1907. No works, with a long preliminary history, such as those at Monterrey, can rightly be said to be due to any one individual; many engineers contributed to the final result, and the writer willingly acknowledges his indebtedness to the able men, who, for ten years prior to the construction of the works, investigated the particular problems which were met--problems which were not only of an engineering and physical nature, but racial and financial. The responsibility of constructing the works in their present form, and leaving them practically complete, did, however, fall on the writer's shoulders.