roasted blende containing 47 per cent., 33 to 34 per cent. The difference is due to the presence of the small quantity of sulphur previously mentioned.

The spelter works deliver about 65 hundredweight of metal per day to the rolling-mill, where it is remelted in a reverberatory furnace and run out into shallow moulds of various sizes according to the gauge of sheet metal on which the mill is running. After passing through the rolls till reduced to the proper thickness, and having been previously annealed and trimmed, the sheets are packed in casks containing 1200 lbs. each.

TOPOGRAPHY WITH ESPECIAL REFERENCE TO THE LAKE SUPERIOR COPPER DISTRICT.

BY JOHN F. BLANDY, M.E.

It is not my intention in this article to consider this subject in the light of the geographer or geologist, but rather in that of the mining engineer, and to endeavor to show the necessity and value to him of studying the minor details of the field or district in which he may be engaged. It has been said by a distinguished geologist that "the natural boundaries of the geographer are rarely described by right lines. Whenever they occur, however, the geologist may look for something remarkable." And again: "Physiognomy is no idle or doubtful science in connection with geology. The physiognomy of a country indicates almost invariably its geological character."

Our country furnishes examples enough of the truth of these remarks, and in no part of it is it so beautifully illustrated as in our own State, which has been so ably described by Prof. Lesley in his admirable little work on the "Topography of Coal."

As the great mountain lines become guides to the geologist in determining and mapping out the geography of the formations, so do the minor details of topography become guides to the mining engineer in conducting his explorations, discovering of dislocations, and determining the character of the deposits which are the object of his search. It is therefore requisite that he should, whilst making his surveys, pay the strictest attention to every variation of the landscape and surface of the ground. Until he has mapped out every feature he may be unable to read the geological changes which may have

passed under his view. In particular he should note all sudden changes in the course of streams, any prominent knolls of ground, and the different angles of slopes of the hills, as they often tell the direction of the dip of the rocks even though the rocks may not be visible. Knolls, forming with each other regular lines, mostly denote the presence of a hard stratum of rock, the character of which it may be valuable to know. The exact mapping of such knolls is necessary to the discovery of displacements in the strata, in a region where fracture veins are found; and on the contrary, should such displacement in the line of knolls or outcropping of a belt be found, then it is a sure indication that such fracture veins do exist. It is hardly necessary to give in detail the many results to be derived from an accurate noting of every natural feature. We may feel sure, however, that there is a natural reason for the existence of every such feature just where it is found-a reason why the stream runs on one side of the valley and not on the other; why it is rapid at one point and gentle in another, and why the hill is steep on one side and slopes smoothly away in the opposite direction.

In illustration of these assertions, I wish to draw attention to a field in which I have been more especially engaged, and to the topography of which I have devoted more or less study, viz.: The Lake Superior copper region.

The Lake Superior copper region has in accordance with the centres of mining industry, been divided geographically and politically into three sections, namely: "The Point," "Portage," and 'Ontonagon" districts, situated respectively in Keweenaw, Houghton and Ontonagon Counties, and although the districts are situated on the same continuous mineral range, they are separated by large comparatively unexplored territories. This division into three sections is by no means accidental, but is the result of the topographical features of the region, as indicated both by its geography and the character of its mineral deposits.

In the first section or district you have natural harbors in the very edge of the mineral range; in the second the range is intersected by a lake which affords transportation directly to the mines; and in the third the mouth of the river, which drains the district, has been made the common commercial centre.

Upon examination, the topography of the range and character of the deposits will be found equally various.

The main features of the coast line of Lake Superior is the great point projecting far out into it from the southern shore. This is the

mountain ridge of copper-bearing trap, which has withstood the action of the forces that have worn away the sandstones around it. The conspicuous points of this great headland are Mounts Houghton

and Bohemian, peaks of the southernmost of the two ridges, which in this section (The Point) constitute the mineral range. These two peaks, with the ridge connecting them, are a great mass of porphyry, and around them on the north the trap range sweeps with a nearly regular curve from the northeast, where the strata have a bearing of about S. 60 degrees E. and N. 60 W., to the northwest, where they have a bearing of about N. 30 degrees E. and S. 30 W. This latter course is maintained on through the Portage district, and with slight variations on through the Ontonagon district.

In the Point district, the greenstone strata is the most conspicuous belt among the traps, and presents a splendid escarpment towards the south of many miles in length. Its excessive hardness has enabled it to resist the forces which have worn off the other beds, and it is now the great landmark of the explorer. It is a base line from which he measures and numbers the other belts to the north and south.

A careful mapping of this ridge, together with its accompanying and underlying conglomerate, enables the engineer to detect the great

displacing fractures which cross the whole range. They seem to possess an approximate parallelism, having a nearly north and south bearing, and as the other veins are displaced by them, belong therefore to the most recent class. They have formed the gorges in the ridge, through which the streams have found their way, and afford easy passage for the roadways. Besides these main fissures you find every few hundred feet other veins of a different class and material. Many of these scarcely show themselves in the greenstone ledge, but are much more prominent in the softer strata, and an accurate tracing of these ledges will often detect their presence and displacements. These are divisible into main or mother lodes, which have a bearing more or less radial to the southern porphyritic mountains, and branch lodes which have their beginning and ending in the main lodes.

This, therefore, becomes the distinguishing feature of the Point district, namely, the fracture veins intersecting the stratification at nearly right angles, in which receptacles have been collected to a greater or less extent the objects of the miner's search. Not all of these fractures contain metallic deposits, or at least in remunerative quantities, and it is a question for the most careful study of the mining engineer to determine, not only by the examination of the mineral contents, but also by the topography of the ground, whether these veins cannot be so classified as to be able at once to know the class to which each one belongs, and therefore approximate to its value. Such an examination will also determine the relative ages of the class, and therefore the comparative method or process of filling, valuable data for the mineralogist. I think it may now be safely asserted that the latest made veins of fracture are those which have caused the gaps of the main ridge, and further, that they are for mining purposes valueless.

In order, however, to study these questions in all their bearings, it is necessary to look at the adjoining districts.

In the second, or "Portage" district, the features of the country are entirely changed. The greenstone ridge has sunk down to the general level of the other strata, or perhaps has disappeared, and the summit of the mineral range is comparatively regular and level. The range is marked by no prominent feature, either of elevation, ravine, or change of course, until the deep gorge occupied by Portage Lake is encountered. The explorations in this section, up to the present time, have discovered but few fissure veins, and those only in the immediate vicinity of Portage Lake. No doubt others will be found, but sufficient examinations have been made to prove that they

are but few and far between, and further, that they belong to the most recent class, and, as asserted above, are to the miner of no value. The workable metallic deposits of this section are the strata themselves, and we are therefore led to infer that the fissures in the "Point" section have there robbed the strata to such an extent as to make them, with local exceptions, comparatively valueless. This point being ascertained, namely, that the metallic deposits in the fissure veins came directly from the inclosing strata, supplies the geologist with a groundwork for his reasoning as to its original

source.

If we now examine closely the gorge of Portage Lake, we will find that its topography opens up other questions of great interest. It intersects the range on a nearly east and west line, the ridge rising on the north side to an elevation of 600 to 650 feet, and on the south side to about 500 feet. The whole slope of the mountain on the north side is covered with the deep deposits of the Drift period. This has been furrowed with deep ravines by the streams which now and formerly ran down the face of the hill. The opposite mountainside has been scoured clean by the current which must have set through the gorge, leaving the rocks with scarce soil enough for vegetation. The gorge, after passing through the main range in either direction, has a bearing nearly north and south, and it is interesting to follow the hillsides, and notice where the force of the current has either left the rocks bare or allowed the deposition of débris. About 50 feet above the present level of the lake, in the town sites of Hancock and Houghton, the ancient shores of the lake are distinctly visible as terraces, extending on the north side from about the middle of section 27 near two miles to the middle of section 25, where the ravines of the mountain-side have made it no longer traceable, and on the south side, from the Dacotah Creek eastward to the east side of section 31, about two and a half miles. The terrace on the north side is higher than on the south (but I cannot now give the difference in elevation), an evidence that a great fracture exists under the bed of the lake. They are not horizontal, as they must of necessity have been at one time, but rise very perceptibly towards the east, an evidence that the mountain range has been subject to some elevating power at a comparatively recent geological period. On the eastern half of section 36, on the south side of the lake, the terrace changes its line of grade, it rising from that point eastward faster than its descent toward the west. This change of grade is a proof of some local disturbance beneath, and it was to me