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north of Tucson, ia a peculiar circular elevation, strikingly like the crater of an extinct volcano. It rises 432 feet *bove the surrounding plain, and its cavity ie three-fourths of a mile in diameter. Its interior walls are so steep that animals once entrapped within them never escape, but leave their bleached bones at the bottom. The rim of sandstones and limestone it uniformly uplifted on all rides at an angle of 40°, while the bottom lies at a depth of from 50 to 100 feet below the general leve of theplam. Although the cavity is crateriform, no lava, obsidian; or other volcauic product was found. Small meteoric fragments were scattered over an area about a third of a mile in length and 120 feet wide, extending north-west and south-east. Exactly parallel with it, but about two miles from the base of the crater, were found t vo large masses, one weighing 154 pounds, and the other 201 pounds, which were on exhibition ; both were deeply pitted, and the larger one was perforated in three places. The latter is now the property of the Ecole des Mines, Paris. Smaller masses were also found, numbering 131 in all, ranging in weight from one-sixteenth of an ounce to six pounds ten ounces. Several of them were coated with aragonite. About 200 pounds of angular sul-phurettea fragments, also or meteoric origin, were found near the base of the crater, a few of which showed a greenish stain resulting from oxidised nickel. A fragment of a mass weighing forty, pounds was examined by Professor 6. A. Koring, who found it to be extremely hard, a day and a-half being taken in making a section ; and several chisels were broken in the operation. An emery wheel was ruined in trying to polish it.This led to closer inspection of certain exposed cavities, when small black diamonds were found which cutpolished corundum as easily as a knife separates gypsum. These diamondt are naineralogically of great interest, their presence in meteorites having been unknown until the year 1887,* when two. Russian mineralogists found traces of diamonds in a meteorite mixture of olivine and bronzite. By treating the amorphous carbon in the cavities with acid, a small whited:iamoud, one-fiftieth of an inch in diameter, was found, as well as troilite and d ubreelite. The general mass contained 3 per cent, of nickel. The Widmanstat-tian figures were not regular. The indications are that a large meteorite, weighing about 600 pounds, had become oxidised in passing through the air, ami had burst before reaching the earth. It is scarcely credible that tfie crater could be acci mted for by meteoric impact, and its origin is a problem unsolved. The fact of special interest may be accepted as proved, that diamonds have been found in meteoric fragments. The specimens were carefully examined by the geologists present at the reading of Professor Foote’s paper, and while there were many opinions expressed as to the so-called crater, and as to its relation to the meteor, none doubted the genuineness of the diamonds;the bisks being practically indestructible; and as the material is purely a waste me, the cost need not be much above the labour of making the sand moulds for casting. Taking the mechanical possibilities of the matter into consideration, there is a good opening for the profitable manipulation of slag, and blast-furnace managers should give tho matter some consideration.THE THEORY AND PRACTICE OFMETALLURGY.*By Professor W. C. Roberts-Austen, C.B., F.R.S.The selection of Cardiff as a place of meeting of the British Association led to the presidency of Section B being entrusted to a letallurgisfc. It will be well, therefore,to deal in this address mainly with considerationscon-nected with thesubject to which my life has been devoted, and I hope that it maybe possible for me to show that this practical art liar both promoted the advancement of science and has received splendid gifts in return. It is an art for which in this country we have traditional love; nevertheless the modes of teaching it, and its influence on science, are but imperfectly understood and appreciated. Practical metallurgists are far too apt to trunk that improvements in their processes are mainly the result of their own experience and o lervation, unaided by pure science. On the other hand, those who teach metallurgy often forget that for the present they have not only to give instruction in the method of conducting technicaloperations, but have truly to educate by teaching thetrchemistry of high temperatures, at which ordinary reac tions are modified or even reversed, while they have further to deal with many phenomena of much importance, which cannot, as yet, be traced to the action of ele menbsin fixed atomic proportions, or in which the direct influence of the atom is only beginning to be recognised. The development of a particular art, like that of an organism proceeds from its internal activity ; it is work which promotes its growth and not the external influence of the environment. In the early stage of the development of an industry the craftsmen gathor a store of facts which afford a bask for the labours of the investigator, who penetrates the circle of the “mystery” and renders knowledge scientific. Browning, inspired by the labours of a chemist, finely tells us in his Paracclsiis .—►To knowRather consists in opening out a way Whence the imprisoned splendour may escape, Than in effecting entry for a light Supposed to be without.If it be asked who did most in gaining the industrial treasure and in revealing the light or chemical knowledge, the answer is certainly the metallurgists, whose labours in this respect differ materially from others which have ministered to the welfare of mankind. First it may he urged that in no other art have the relations between
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Iron
London, Middlesex, GB
Fri, Sep 11, 1891
Page 26
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