Thus it will be seen that every student who has worked in the laboratory during the last year has not only had a definite work of his own to do, but has also had the opportunity to watch or to assist in a very considerable variety of other work.

2. Advantage to the Student of having a part of his Practical Work in the Curriculum of his School.-We learn by our mistakes. Men can try, and fail; can find out usually why they failed; can repeat the work with the failure in part or in whole corrected. They can learn economy by their own lack of it.

Large works cannot afford to spoil a charge to show a student what happens from a little carelessness. A well-regulated establishment may go on a long time without such a slip, and unless the superintendent is used to giving instruction, and takes pleasure in it, the student may be months at a works without finding out what the key to the success of the establishment is.

Again, a student learns the value of chemistry as a check upon metallurgical work. Who would attempt to run a blast furnace on lead ores or on iron ores without knowing something about the composition of slags and of the fluxes at hand? The students here plan the proportion of the fluxes to be used from their own analyses of the same. And if they find from their reading that a slag of 30 per cent. SiO2, 45 per cent. FeO, 15 per cent. CaO, 10 per cent. Al, O,, should give a good fusion and a slag clear of lead, they put in fluxes containing these elements in the above proportions, and when they get through they analyze their slag, to see if they got what they tried for, and to see if it was as lean in lead as they wished it to be.

But perhaps the greatest advantage of all to the student, and the one which will stay with him through his whole life long, is the spirit of investigation which is awakened by his work, and which is made evident by the questions he asks and by the zest and intelligence with which he carries on his work. This we consider has been proved beyond all question.

We wish to disclaim any pretensions which we may be supposed to have that this laboratory is in any sense of the word a substitute for the works. What we do claim is that it prepares students to go into works and profit by them.

3. Advantage to Works.-We have already noticed one advantage, viz., that the men have had a chance to test themselves and find out where they are weak. There is, however, another advantage which may grow out of their experience in the laboratory. These men are used to testing processes on a small scale, and if they are,

when older, called upon to erect costly works and to devise new and expensive processes, they will naturally spend a thousand or two dollars in trying the process practically. Most of us are familiar with large and costly failures which might have been prevented if the process had been studied in this way. For while work on the small scale does not pretend to deal with the relation between the cost of production, of transportation, and the market value, it does test most thoroughly the chemical and mechanical principles on which the process must depend. Again, this practical work enables us to make a far more just division of hand-men from head-men than could possibly be made from recitations and examinations alone. And if we have an application for a mau who may by-andby be needed to superintend, we recommend a very different man from what we do when we were asked for an analyst or a surveyor.

Advantage to Mines of having their Ores treated in the Laboratory. -We will cite one example. The Merrimac Mine of Newburyport has recently called an engineer from a distance to systematize their smelting works. He informs me that the figures furnished by the students were of very great value to him in planning his ore charge. And again, as soon as the mine is prepared to establish washing-works, and the matter is under consideration at the present time, the results of our washers will be at their service.

To sum up what has been said: We believe that such a course of instruction will bring out latent originality if a student has anything of it in his composition, and that, if he is nothing but a copyist, his instructors, as well as the man himself, will be convinced of the fact before he leaves his school; and again, that such instruction will enable him to profit far more by his visits to works, or studies in them, than he otherwise would.

The testimony of graduates of the school and of their employers bears us out in the above statements.

4. Degree of Accuracy of working Ores on the Small Scale as compared with the Large Scale.-On the large scale the operations are continuous. If a little is left by one charge, it is taken up by the next one, and does not affect the total. On the small scale, however, what is lost in one charge by carelessness is not picked up by the next, because there is no next charge to follow it. In large works men are chosen to fill places by their skill or aptness for those places. On the small scale the students spend a part of the time of doing the work in learning how to do it. To be sure, they learn vastly quicker than the ordinary hands who are usually employed for such work; but

still this does not wholly make up for their lack of skill in the first instance, nor does it make the small works quite on a par with the large ones in this respect.

5. Results of Work in the Laboratory.-The following examples will serve to show the kind of work that is done by the students, as well as the scale of it and the degree of accuracy attained.

A lot of poor ore from the dump heap of the Merrimac Mine of Newburyport, weighing 8485 pounds, was crushed and washed to separate the argentiferous materials from the gangue rock, and yielded these proportions:

Referring this yield to one ton of crude ore, the intrinsic value of the metals in the products obtained from it would be:

1. Smelting ore, 147.14 lb., containing 39.4 per cent. lead, or 57.92 lb, or $3 47

2. Middle-grade ore, 429.8 lb., containing 9.11 per cent. lead, or 39.15 lb., or $2 35

The ore itself was valued for lead and silver, but not for gold, with this result:

1 ton contained 5.23 per cent. lead, 104.6 lb.,
.02 per cent. silver,

.4. "

The values of the above products would be:

$6.28
6 42

$12 70

1 ton smelting ore,. 39.4 per cent. lead, 788 lb. $47 28
"2 silver, 20.41 oz. 23 47
gold, .6998 oz. 14 42

.07
.0024

A lot of lead ore, composed chiefly of galena with a little pyrite, blende, quartz, and feldspar, from ore of the veins crossed by the Burleigh tunnel of Georgetown, Colorado, was roasted, agglomerated smelted, refined, and cupelled. It gave the following results:

Ore,

1100 lb. @ 67.37 per cent. lead, 675.07 lb. .095 66 silver, 15 24 oz.

After roasting and agglomerating, 996 lb. @60.68 per cent. lead, 604.52 lb. .086 "" silver, 12.48 oz.

After smelting and refining to soft lead, 429.75 lb. @ 98.95 per cent. lead,425 24 lb.

From which it appears that the loss in roasting and agglomerating was 70.55 pounds lead and 2.76 ounces silver; smelting and refining was 179.28 pounds lead, and .15 ounce silver. This loss in silver is too little to represent the truth, as 12.33 ounces is known to be too high; the sample was taken from the tops of the pigs.

The zincing was accomplished by stirring in one per cent. of zine with melted lead, and then casting it in ingots and sweating it. This operation was repeated three times, and each time yielded a rich argentiferous zinc dross and a poorer zinciferous lead; the actual weight of silver in each of these six products is here given:

429.75 pounds refined lead, @.197 per cent. contains 12.33 ounces silver. 1st. Argentiferous dross, 9.73 ounces silver (a little high), sample poor.

1st. Sweated lead, .

This last sweated lead contained but .001 per cent. of silver. The distilling and final cupelling were not as successful as the rest, as from breaking of the cupel and other mishaps only 9.73 ounces of pure silver were obtained.

A copper ore from Sante Fe was worked by a student who was preparing himself to go to the mine. His main object was to experiment on slag, to find out a suitable composition that would yield soft, clean copper in the blast furnace.

The ore was composed of malachite, chryscolla, cuprite, atacamite, with a very large quantity of grossularite (lime garnet), and also quartz, calcite, and a little pyrolusite. Its chemical composition is given in the table below.

The run was divided into halves; after the first was through, the furnace was run out and then charged up again with a new mixture. During the first run the slag was planned to carry a high per cent. of iron, during the second run it was planned for a high per cent. of lime.

It will be noticed at once in the first-run slag as obtained a monstrous deficiency in FeO. This will be accounted for by the pig copper from this run, which contained 18 per cent. iron.

The second run was much more nearly adjusted to suit the furnace reactions, as is shown by the slag, which is not very far from the plan, and also by the copper, which was soft and malleable, and contained but .3 per cent. iron.

AN EDGESTONE CRUSHER FOR ANALYTICAL SAMPLES. BY ROBERT H. RICHARDS, PROFESSOR OF MINING, MASSACHUSETTS INSTITUTE OF TECHNOLOGY, BOSTON.

(Read at the Amenia Meeting, October, 1877.)

DURING the summer of 1870, I had an opportunity to visit the laboratory of the late David Forbes, Esq., in London, and was much interested in a labor-saving device which he had attached to his agate mortar. The mortar was placed in the centre of a small table, and about ten inches to the right of the mortar, a post, perhaps two