The writer herein claims no new principles, but merely the applications of some very old ones, and as yet in a somewhat imperfect way, to the ordinary operations of machine shop practice. Such a reform as is here foreshadowed is most urgently needed as one of the means of systematizing the work of the mechanical engineer. It is, in fact, only the common sense use of methods which have long been employed by the geographer, the topographical-engineer, and even by the landscape-gardener and the railway

contractor.

DRIVEN WELLS.' By J. C. HOADLEY, M. E., Boston, Mass.

[ABSTRACT]

THE investigations of Darcy, Dupuit and Lueger, and the experimental determinations of Piefke and others, relating to the flow of water in porous earth, are recognized. Some unfounded assumptions, and fallacious theories and unsound explanations of these, by courts and experts, are pointed out. Description of the method of conducting experiments which should place in a clear and convincing light the truths of nature, relating to the flow of water from the natural height of the surrounding ground water, down an obstructed hydraulic slope, by gravity alone, to the depressed surface of the water immediately around the suction pipe of a pump and in wetting contact therewith, whether such suction pipe be driven or otherwise inserted in the ground, or put into the open water of an ordinary well :

First, by pumping from actual tubular wells inserted in natural water-bearing soil, and marking the effect both as to the quantity of water obtained and slope of water-surface produced, in comparison with corresponding results by similar pumping from a small open well; and, second, by laboratory experiments with pumps, working under various conditions in artificial filtering tanks, supplied with appropriate measuring, indicating and recording appa

ratus.

1 This paper is printed in full, with illustrations, in the Sanitary Engineer for De cember 4, 11, 18, 25, 1884.

Special points of investigation were:

1. As to the alleged difference between open wells and driven wells in point of efficiency in obtaining water from the ground. As to the alleged difference in the same respect between pipes driven tightly into the ground "without the removal of any earth upward," and similar pipes under like conditions inserted loosely in holes bored for them.

3. As to the alleged newly discovered "principle," or "power of nature," according to which, it is alleged, a pump producing a partial vacuum in a suction-pipe, may, provided the suction-pipe be "driven tightly into the ground," cause water not in contact with the exterior surface of the suction-pipe, to flow towards the pipe, and up to wetting contact therewith, otherwise than by the force of gravitation causing it to percolate through the pores and interstices of the soil with a rapidity proportioned directly to the slope, i. e., to the difference of level produced by pumping, in a given horizontal distance, and inversely, to the obstruction of the soil.

4. To ascertain as far as possible, by direct experiment, the form of the curves of such obstructed hydraulic slope.

The true theory of the flow of underground water as set forth by the physicists first above named, fully sustained by the results of the experiments, and the pretentious fallacies above referred to completely refuted.

ON A NEW METHOD OF PRODUCING SCREWS OF STANDARD LENGTH AND UNIFORM PITCH. By PROF. Wм. A. ROGERS, Harvard College Observatory, Cambridge, Mass.

[ABSTRACT.]

DESCRIPTION of the process by which a half-meter screw of the dividing engine constructed for Prof. W. A. Anthony was made, together with a discussion of methods by which further improvements may be made.

DEVELOPMENT OF THE PHILOSOPHY OF HEAT ENGINES. BY PROF. R. H. THURSTON, Stevens Institute, Hoboken, N. J.

[ABSTRACT.]

THIS paper presented an historical sketch of the development of the modern, and the now accepted theory, of heat engines, including the study of wastes. This paper was read at Montreal before the B. A. A. S., by request, and was offered in Section D, of the A. A. A. S. by request of members of the Section.

THREE PROBLEMS IN RIVER PHYSICS. BY PROF. J. B. JOHNSON, Washington University, St. Louis, Mo.

In the past five or six years, there has been a great deal of money spent upon, and study given to, many questions of a scientific nature pertaining to the improvement of our western rivers. Your attention is called to some conclusions that may be drawn from recent investigations on the three following problems: I. The Transportation of Sediment and the Formation and Removal of Sand-bars.

II. The Flow of Water in Natural Channels.

III. The Relation of Levees to Great Floods, and to the Low Water Navigation of Rivers.

I. The Transportation of Sediment and the Formation and Removal of Sand-bars.

The solid matter carried by streams of variable discharge and cross-section, flowing over sandy beds, is at once the cause of, and remedy for, most of the obstructions to the navigation of such streams. A proper understanding of this subject is a prime requisite to an adequate conception of the conditions governing the flow of water in natural channels, the improvement of low water navigation, flood confinement, etc.

In all natural water courses, the material carried by the stream may be graded according to the method of its transportation, as, First, That carried in continuous suspension.

Second, That carried in discontinuous suspension.

Third, That carried by rolling on the bottom.

Sediment in Continuous Suspension. This is composed of such finely divided particles of clay and mud that any slight disturbance of the water in a vertical direction is sufficient to prevent its deposition, and so it mostly remains in suspension until it reaches the sea. A large part of the sediment carried by the Mississippi River is of this class. It mostly comes from the western tributaries, more especially from the Missouri. If a quart of this water be placed in a glass jar, and set away, it requires some ten days for the water to become clear. Evidently, this kind of sediment does not form sand bars, neither can the engineer avail himself of it in building artificial banks in contraction works. It is therefore of no consequence to the river engineer. It is neither helpful nor harmful, and may be ignored.

Sediment in Discontinuous Suspension. This kind of sediment is composed of sand, more or less fine according to the velocity of the stream. It is the material of which sand bars are made, and it is also the material out of which the engineer builds his artificial embankments by the square mile behind his permeable dykes. It is constantly being picked up at one point and put down in another by the action of a law as unchangeable as the law of gravity. In the river's tireless efforts to attain a uniform flow it is constantly scouring out the engorged sections, and filling in the enlarged sections. For any given stage of water, the volume discharged at successive sections is the same, but since the sections do not have equivalent areas, the mean velocity at successive points is a constantly varying quantity. The river undertakes to overcome this inequality and so engages in an enormous carrying trade, which consists in cutting out the bottom where the section is less and the velocity more, and carrying this sand to the first point below where the section is more and the velocity less, and there it is deposited. Evidently, if any given stage of water should continue long enough, this double action of scouring the small sections and filling the large ones would result in a nearly uniform flow, when such small particles as could be carried by the resulting velocity would be so carried in permanent suspension, leaving a bed of tolerably permanent character, being only influenced by the matter rolling on the bottom. But here comes the trouble. No sooner has the river set to work to adjust itself to any given stage, than behold, the stage changes, and then it must go to work, cutting and filling at new points, and as the stage is ever changing, the river is ever beginning anew in its endless task.

width. Take an actual case.

It may not be clear why this change in stage should so disarrange matters. Let us see. The cause is the great variation in At Plumb Point, on the Mississippi River, sixty miles above Memphis, the following extremes were found in 1879 on a reach eight miles in length.1

Thus, at low water, the wide section had a mean velocity of 2.65 feet per second, while the narrow section had a mean velocity of only 1.15 feet per second. At a stage 26.6 feet above low water (which in the table here given is called "high water," although it is some eight feet below extreme high water) the conditions are reversed, for now the wide section has a mean velocity of 3.67 feet per second, while the narrow section has a mean velocity of 10.1 feet per second. Here the wide section was some eight miles above the narrow one. Evidently the river is cutting out the shoal and filling up the pool in low water, and cutting out the pool and filling on the succeeding shoal in high water, and in fact this is what is always observed to occur.

The amount of this local scour and fill on the Mississippi river is enormous. In the case above noted there was a total scour over the reach of 350,000,000 cu. ft. or enough to cover one square mile to a depth of 11 feet. This occurred from Nov. 13 to Jan. 3. In many cases the rate of fill and scour, as well as the total amount, is much greater than this. It is not uncommon for the shoal places to be built up as much as from six to ten feet in time of high water, so that the bottom of the river is then higher than 1 See Report of Miss. Riv. Commission for 1881, p. 69. 2 From plate 7, p. 120 of same report.