AN article on “The Lochaber Hydro-Electric Power Undertaking”, in NATURE of November 29, 1930 (126, 848-849), described the first and main portion of an engineering scheme of considerable magnitude by which water from a catchment area of 303 square miles in Inverness-shire is being collected and led to a power station at Fort William, near the foot of Ben Nevis, which will have an ultimate capacity of 120,000 horse-powerby far the largest installation of its kind in Great Britain. The first instalment of the undertaking, costing about three million sterling, utilized the natural reservoir in Loch Treig by means of a tunnel pipe line to Fort William, and was completed in 1930. The second in the sequence of three stages of development was commenced shortly thereafter and completed in 1934, at a cost of another million. It forms the subject of a paper read on December 15 before the Institution of Civil Engineers by Mr. A. H. Naylor, who was chief assistant engineer to Mr. B. N. Peach, the resident engineer for the undertaking under Messrs. C. S. Meik and Hal crow of Westminster, the consulting engineers responsible for the design and supervision of the works from their inception. The following information of interest is extracted from Mr. Naylor's paper. Reference should be made to the map of the district which appeared in the issue of NATURE mentioned above.