OBSERVATIONS WITH LYSIMETER; BY E. L. STURTEVANT.

37

terval of time equal to twice the constant distance between pickets divided by the velocity of sound. For instance, if the pickets be four inches apart, or one-third of a foot, the terminal pitch would be one of about 1500 vibrations per second.

The law of retrogression of pitch may be of interest. press it as a function of passing time, let

To ex

t = the time following the initiation of the reflected tone. Then by aid of a diagram we easily obtain the following relation between the above quantities, viz. :

The curve for this equation is not easily classified. But by computing quantities and constructing a curve it is found to be very much like a hyperbola referred to its asymptotes, which indicates that the pitch falls rapidly at first, and less so subsequently.

Not only is the above described phenomenal reflection observed in connection with fences, but from any series of flat surfaces in steps as indeed in the case of stairs under proper conditions. Such echoes have been observed from the steps in front of the State House at Columbus, Ohio.

FOUR YEARS' OBSERVATIONS WITH A LYSIMETER, AT SOUTH FRAMINGHAM, MASS. By E. LEWIS STURTEVANT, of South Framingham, Mass.

THE Lysimeter used was a chestnut frame, strongly put together so as to enclose an area of exactly five-thousandths of an acre. The lower border was furnished with a cutting edge of iron, and by careful manipulation the frame was forced into the soil, to a depth of twenty-five inches, so as not to disturb the enclosed soil. On the upper edge a zinc edging which precisely marked out the area was then put in place. Underneath a bottom was driven; aprons were then placed on the outside of the frame to intercept all water, and to convey it to a level lower than this bottom, finally, a zinc pan was closely affixed to the bottom to catch all the filtration or drip from the area within the box.

The apparatus was completed Nov. 19, 1875, and up to January 1,1880, careful record was made of all the water of filtration. The record of rainfall is that by the Boston Water Works, by whom a station was maintained in close vicinity.

Under the head of evaporation, I include the difference between rainfall and percolation.

The soil, a sandy or gravel loam, in poor agricultural condition, and covered with a sod which had not been disturbed certainly for ten, probably not for fifteen or twenty years. Agriculturally speaking, such a sod would produce a short half ton of hay per acre in a favorable season. Under the eight or ten inches of black loam, a yellow loam. The bottom represents the level of the gravel bed underlying the adjoining soil.

RETENTION OF HEAT BY THE EARTH; BY H. C. HOVEY. 39

From these figures we may assume that, for this region, percolation is practically nil during the growing season, and that leaching, so much dreaded by the farmer, is, under farm conditions, not to be practically feared.

The following is the record by months:

Not being willing to trust a wooden frame any longer, the records were discontinued with 1880, although at this time careful examination showed the apparatus to be in good order.

A REMARKABLE CASE OF RETENTION OF HEAT BY THE EARTH. By H. C. HOVEY, of New Haven, Conn.

[ABSTRACT]

THERE is an area of about two acres, in Pictou county, Nova Scotia, where the snow never lies long without melting, and the frost, even in severe winters, penetrates but for a short distance. Over it are scattered fused masses of ironstone, resting on the outcrops of what are known as the "Main" and the "Deep" seams of bituminous coal (here about 450 feet apart), and partly on the outcrops of other smaller seams.

The name "Pictou" is from a Micmac word, signifying fire;

and Indian tradition still points to this spot as having once been the scene of a long-continued fire, which made the aborigines avoid the place as visited by the anger of the gods.

The coal-measures of Pictou were discovered in 1798, at the very point now described; and the place was then covered with a bed of ashes, over which grew large hemlock trees. One of these was cut down twenty years ago, and showed 230 rings of annual growth. Three feet under the root was found a piece of wood fashioned by some kind of axe.

Last spring, Mr. Hudson, manager of the Albion mines, found it necessary to sink a pit on this area, at the outcrop of the Deep Seam, to facilitate ventilation. The heat of the ashes, thirty feet below the surface, was immediately tested by a reliable ther mometer and was found to be 80 degrees Fah., at a time when the surface temperature varied from a minimum of 45 degrees to a maximum of 65 degrees. Soon after an opening had been made, the air currents caused the temperature to fall to the normal point. Mr. Edward Gilpin, Government Inspector of Mines, examined this pit, and kindly placed at my disposal the foregoing facts, together with a comparative view of sections of the same strata, made only a short distance apart; the design being to exhibit the changes made by igneous action.

The present section is taken at the new pit on the burnt area; and the original section is from the Geological Survey of Canada for the year 1869, p. 69.

The surface cover of clay is changed to a reddish, coherent mass. The small portion of the 144 feet of black shale, passed through by the shaft, is transformed to hard scoriæ.

The upper part of the Deep Seam of coal is completely burned away, leaving a compact, laminated, reddish ash; and in this ancient bank of ashes, known to be over 300 years old, the retention of heat was observed which it is my object now to put on record.

TIME SERVICE OF CARLETON COLLEGE OBSERVATORY.

W. PAYNE, of Northfield, Minnesota.

By WM.

THE purpose of my remarks is not to bring before the Association anything that is particularly new to science in principle, but rather, at the solicitation of friends, to place on record that which is being done in the way of time service in the new field of the northwest. As prefatory to this, please indulge me in a very brief statement respecting the location and instrumental equipment of the College Observatory.

The Observatory of Carleton College is located at Northfield, Minn., forty miles south of St. Paul, on one of the main lines of the Chicago, Milwaukee and St. Paul railway. The building was erected in 1878. Its latitude was determined by Prof. B. F. Thomas (now of the University of Missouri), in 1879, by a series of observations made with a two-inch Wurdemann zenith telescope, loaned to the Observatory for that purpose, by Lieut. Edw. Maguier, Chief Engineer of the Dept. of Dakota. By using the Talcott method, Professor Thomas found the latitude of the Observatory to be 44° 27' 41". During August 1880, the work was done a second time by myself using the same instrument and method, observing forty pairs of stars, on different nights, with mean places from Safford's catalogue. After the proper reduction the latitude was found to be 44° 27′ 40′′.8. These two determinations of the latitude, being a year apart in time, and wholly independent of each other were in surprisingly close agreement. In Oct. 1880, by the aid and courtesy of the officer last named and Lieut. O. B. Wheeler, of the Lake Survey, the longitude of the Observatory was determined, the Coast Survey meridian of St. Paul being used as the base of operation. Observations were taken at Northfield and St. Paul on succeeding nights, and telegraphic signals were exchanged. Independent reductions of these observations showed the longitude of the Observatory to be 1 h. 4 m. 23.8 west of Washington, and 14.3 west of the meridian of St. Paul.

INSTRUMENTS.

The Observatory is furnished with the following instruments :A Clark equatorial, 84 inch aperture, 10 ft. focal length with complete mounting.