COMPARISON OF RAIN GAGES.

Studies of long term rainfall records in the vicinity of New York city and upon Long Island* have made it plain that in some cases the smaller precipitation recorded in early years was due to the use of less perfect types of rain gages than those used commonly during the past ten or twenty years. A series of experiments has therefore been begun at my request, in which duplicates of the type of gages used in the earliest observations have been constructed and exposed side by side with modern gages. One set of these experiments is being carried on at the weather bureau station at Cornell University, Ithaca, N. Y., and another set at the Clarkson Memorial Institute at Potsdam, N. Y.

There was an unfortunate delay in the completion of these gages prior to the remarkably heavy rainfalls of last September and October, and thus the number of comparisons in individual storms obtained up to the present time is not sufficient to be at all conclusive. The observations are being continued and forms a part of the work provided for under the specifications and appropriation of the Fuller bill.

LARGER RUN-OFF OF THE SACANDAGA DRAINAGE AREA.

Even after the most careful review of all existing records, the rainfall upon the several portions of Adirondack watershed remains at present not well determined, and awaits longer records and the few years records from additional stations recently established.

Meanwhile, I have had to draw the isoheytals of plate 10 with somewhat of a bold sweep from the compensated records of the several rainfall stations after a study of the elevations shown on the topographic maps and a consideration of the lay of the land in relation to the probable general course of the vapor-laden winds for the same period. Since preparing this isohyetal map, my attention has been called to a similar map in the U. S. Monthly Weather Review for January, 1907, by Mr. R. E. Horton, in which I am pleased to find very much the same conclusions are independently reached. These rainfall records and isohyetal maps make it plain beyond a doubt that the Sacandaga rainfall averages about five or six inches larger than for the Hudson above Mechanicville as a whole, and it is also certain because of greater average altitude and the probable larger per cent. of forest cover that the evaporation loss is less. Therefore, the Sacandaga run-off must be decidedly larger than that at Mechanicville.

I am led to believe from the data shown on our preliminary isohyetal map, that the average annual precipitation on the Sacandaga drainage is at least forty-nine inches, being less than 45 inches at the easterly end and more than fifty-five inches at the westerly end, and that the average rainfall is probably somewhat in excess of the mean values shown by the stations heretofore observed, because of the greater precipitation on the hills and mountains than in the valleys where the older rain gages are located.

The mean annual rain fall for the entire Hudson basin above Mechanicville is probably about 43 inches. If so, the precipitation on the 1,050 square miles of Sacandaga drainage is six inches larger than for the entire area of

*See Burr-Hering-Freeman Report on Additional Water Supply for New York City 1900 p. 683 et seq.