succeeded in making a pair of crown and flint disks, 23 inches diameter, of very great excellence. Surely we have the material, the fuel, and the skill in this country to make optical glass as well as the finished objectives for all our astronomical instruments.

Lengthy as this paper has become, I confess I have only skimmed over the subject, passing by much which might be of interest, much which would make it of greater value as a paper of reference; but the theme in itself is too great to be treated as it should in a paper like this; for when we consider that it is through this self-same "optic glass" we have learned the marvellous "story of the universe," the complete story is certainly worthy of a place in our annals.

"Go to yon tower, where busy science plies
Her vast antennæ, feeling thro' the skies;
That little vernier, on whose slender lines
The midnight taper trembles as it shines,

A silent index, tracks the planets' march

In all their wanderings thro' the ethereal arch,

Tells through the mist where dazzled Mercury burns,

And marks the spot where Uranus returns."

DCCLI.*

A CONVENIENT FORM OF WIRE-TESTING MACHINE

BY ARTHUR L. RICE, BROOKLYN, N. Y.

(Junior Member of the Society.)

THE use of a small and inexpensive testing machine is often desirable for the purpose of illustrating the action of the various metals under stress, or for the testing of wire and small specimens and for the testing of small cast-iron samples in the foundry to determine the quality of the iron used.

A description of such a machine which has been in use by the writer for the past year may be interesting to the Society.

To be available, the machine must be convenient to handle and read, must have sufficient strength, must record the breaking load, and must have little or no shock at breaking. Above all, it must be cheap to build.

The resulting machine is shown in Fig. 14. The spring-balance dial and hand wheel are convenient to each other, and the machine is mounted at such a height from the floor as to make the scale easily readable. The details of the pulling-gear construction are shown in Fig. 15. The spring balance with a recording hand seemed the most convenient and available method of measuring the load; to avoid the rebound of the balance, an air dash-pot was introduced and has worked satisfactorily. The details of the dash-pot and pulling clamps are shown in Fig. 16. On account of the cup-shaped washer the leather on the dash-pot piston can be made so loose a fit that the piston will drop of its own weight, thus eliminating all error from friction. A small outlet with cover is provided at the top of the dash-pot, so that the amount of the cushioning can be regulated as needed. The pulling clamps are along the lines of the ordinary designs for small machines.

For bending tests a yoke is arranged as shown in Fig. 17, and

* Presented at the New York meeting (December, 1897) of the American Society of Mechanical Engineers, and forming part of Volume XIX. of the Transactions.

the lower grip head is changed for a knife edge; specimens can be tested either as cantilevers, by clamping one end fast to the beam of the yoke, or with a support at each end.

The machine has given excellent satisfaction, is convenient to handle, and works well up to its full capacity, 200 pounds. The cost of twelve machines complete was only about $380, or $31.75 apiece.

DCCLII.*

A BOILER SETTING.

G. W. BISSELL, AMES, IOWA.

(Member of the Society.)

THE sketch presented herewith (Fig. 18) shows a method used by the writer about two years ago for supporting a horizontal return tubular boiler, fifty-four inches in diameter by sixteen feet long.

Two pairs of lugs of special design are attached to the sides of the shell above the fire, and at a distance, to centres, of three feet six inches from the ends of the shell. These lugs rest on hangers of one-inch round iron, which are carried by nuts on wrought-iron saddles cut from three-by-one-inch flat bar iron. These saddles rest on I-beams. At the front end of the boiler one seven-inch beam is used. At the back end the saddles are supported by an eight-inch equalizing I-beam five feet long, which rests on a one-inch roller which has a bearing on a nineinch I-beam. The latter, and also the seven-inch I-beam at the front end, rest on pairs of columns for which six-inch channel beams are used. Suitable castings serve as sole-plates for the I-beams and as caps for the columns.

Cast-iron plates twelve-by-twelve by one and one-half inches serve as foot plates for the columns.

These plates are set perfectly level on piers of brick-work about two feet square, built independently of the boiler setting proper.

Tie-rods of three-quarter-inch round iron hold the columns to place at the top. Longitudinal stability is afforded by setting the channels into the brick-work of the boiler setting, so that the flanges do not project, but are flush with the wall.

It is thought that the following advantages are possessed by this design over others in more general use:

* Presented at the New York meeting (December, 1897) of the American Society of Mechanical Engineers, and forming part of Volume XIX of the Transactions.