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feet high, was firmly fixed to the table. Hinged to the top of this post was a lever arm, extending horizontally towards the left; and at a point in this lever, which was vertically over the centre of the agate mortar, an upright rod was attached, and in the lower extremity of the rod the agate pestle was firmly inserted. The apparatus was completed by having a weight hung on the left or outer end of the lever. The pressure of this weight was multiplied by the lever and transmitted to the agate pestle through the upright, and thus saved much of the labor needed in ordinary agate mortar crushing.

The ideas derived from this mortar in use in Mr. Forbes's laboratory, and from the use of an edgestone mill or Chilian mill for crushing ores in the mining laboratory of the Institute of Technology, have taken form in the instrument I am about to describe.

The edgestone for laboratory work

consists of an agate wheel rolling upon an agate slab, and pressed down upon the latter with great force by a common elliptical carriage spring which is screwed to the ceiling. The crushing power is so great that grains of quartz 1-12 to 1-10 inch in diameter may, by rolling the wheel over them to and fro a half dozen times, be so comminuted that seventy-five per cent. of the whole will immediately pass through a 1-100" mesh sieve. The agate plate is, in length, breadth, and thickness, 6" X 4" x 1", the wheel is 3" in diameter, and 1" thick, and revolves on a steel axle 3" thick.

It is mounted in a Y or fork much like that used for the front wheel of a bicycle. Above the fork, the metal is rounded and smoothed to serve as a handle. A wooden joist 2" x 2" transmits the pressure of the spring to the wheel.

I cannot yet tell with certainty what the quantity of work that it is capable of doing may be, or the variety. In a single trial, a lot of quartz sand, which at the start would pass through 1-12" mesh sieve, and mostly rest on 1-16" mesh sieve, weighing 92 grams, was

wholly, to the last grain, put through a 1-100" mesh sieve by me in half an hour, without assistance in sifting, etc. fact that it was necessary to put the last grains much better record could have been made.

Were it not for the through the sieve, a

Upon oily substances it will probably do little work. It squeezes the oil from Indian corn, and then refuses to roll.

In regard to the contamination of the sample by silica, the obser vations thus far tend to show that this takes place much less here than with the grinding action of the agate mortar. In one instance some pure crystallized corundum was crushed, and the face of the plate seemed but little touched by it. It seems probable on this account that steel, for most purposes, might be used as a substitute for agate.

A steel wheel and plate complete would probably cost ready for use from $12 to $20, according to the finish. The total cost of the agate apparatus in use by me, owing to inadvertence on my part, cost very high. Its details were as follows: plate, $13; wheel, $13; machine work, $12; spring, $1; woodwork, $1-total, $40.

The advantage of grinding action over rolling for crushing minerals needs hardly to be considered in discussing the economy of this wheel as compared with the agate mortar, yet with the 25 or perhaps 50 per cent. advantage which the agate mortar may have, this sinks into insignificance when compared with the advantageous circumstances under which the wheel is placed.

NOTE UPON THE COST OF TWO BLAST FURNACES IN THE CLEVELAND DISTRICT IN ENGLAND.

BY P. BARNES, PLAINFIELD, NEW JERSEY.

(Read at the Wilkes-Barre Meeting, May, 1877.)

IN vol. 33 of the Proceedings of the Institution of Civil Engineers, London (part 2, for 1870-71), may be found a statement of the cost of two blast furnaces, together with a somewhat detailed description.

The attempt will be made in this note to restate these items of cost, so that the information may be rendered perhaps more accessible to our members than in its present place of record, and also in order that the items may be more intelligibly compared among themselves, or with similar items in other cases.

The leading dimensions, etc., of these furnaces are as follows :

NOTE UPON THE COST OF SIX REGENERATIVE FURNACES, BUILT IN 1875 AT THE EDGAR THOMSON STEEL WORKS, NEAR PITTSBURGH,

FOR HEATING STEEL INGOTS AND BLOOMS.

BY P. BARNES, PLAINFIELD, NEW JERSEY.

(Read at the Wilkes-Barre Meeting, May, 1877.)

THESE furnaces are of the ordinary Siemens type, and present no special peculiarities of construction. The bed of each is 8 feet by 20 feet clear inside of the walls and ports. The producers are placed at a distance of about 200 feet from the furnaces, and the gas is collected in an iron tube and led across the yard overhead. It then drops underground into the gas flue, and is distributed to the furnaces. A considerable weight of floor-plates over the valve-pits is included in account 39, but none of the general stock of floor-plates for the mill were charged to the furnaces.

In Table No. 1 is shown the money cost of the furnaces as distributed to the several accounts named.

In Table 2 is shown the proportion of each account due to each of the several items or classes of expenditure named.

It is thus rendered possible, almost at a glance, to determine the money value in this particular case of each of the items named. The regular work of three of these furnaces in heating steel blooms for the months of January and February, 1877, was 77 rounds per week of 60 blooms each, or 4620 30-foot rails per week. Each furnace will heat 8 14-inch ingots, for three rails each, at one time.