The instrument works best when the chariots, A and B, are about opposite to each other; when they are at opposite extremities of f f and f’ f’ respectively, the pull at P tends to produce a skewing couple.  If the chariot, B, could be put upon f f and work, if needful, by a double parallelogram from m m, we should have, excepting the skew pull, some great practical advantages.  We might throw the whole of the weight of the machine on the one pair of friction wheels, and replace the other pair by a single wheel, the portion q’ f’ f’ q’ of the machine virtually disappearing.  Three wheels, of course, would be a real improvement.  Further, we should have the sum curve and primitive drawn to the same base line, and the simplification in the number of parts ought largely to reduce the cost of the instrument.

To be able to perform “inverse summation” (which in the language of differential calculus is to find y as a function of x, when we are given y=f(dy/dx), and not dy/dx=f(x) as usual), we only want a means of making the plane of the wheel, w, parallel instead of perpendicular to m’ m’, and it is easy to design a modification in the construction which will allow of this change.

I hope the above description of the integraph may have made its construction and method of working sufficiently clear.  Those of you who have a taste for mechanical work, and the necessary tools, might, I think, with some patience, construct a workable integraph.  I expect the pivots would be the hardest part of the work.  I hope, some day, myself to have another instrument made with a more readily changeable polar distance, with trace and guide points working in the same vertical, and a wheel permitting of inverse summation.  If this project is ever carried out, I hope I may be permitted to communicate further particulars to our society.

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After some forty years of immersion in the waters of the pool of Echoschacht, not far from Hermannstadt, several human bodies have been brought to the surface in a state of perfect preservation.

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SOME HINTS ON SPIKING TRACK.

The usual dimensions of track spikes are 51/2 X 9.16 inches square, their weight about half a pound each.  Their common defects are brittleness and imperfect points.  In spiking track, the most important points to be attended to are the proper spacing of the ties and driving the spikes in such a manner that the ties shall be held in place at right angles to the track and the rails in true gauge; to insure the latter, the track gauge should always be used when spiking the gauge side, the rail being held to proper position by a lining bar.  The gauge should be kept about 6 or 8 in. ahead of the tie being spiked and should not be lifted until the spikes are driven home; gauges should be tested regularly and every morning when they are to be used all day, so as to