Feb. lo, 1887] 



NA TURE 



355 



THE INSTITUTION OF MECHANICAL 

 ENGINEERS ■ 

 'PI Hi Institution of Mechanical Engineers held its meeting in 

 the Theatre of the Institution of Civil Engineers on 

 Thursday ami Friday of last week. The paper on "Triple 

 Expansion Engines," read at the last meeting, of which we then 

 gave an a'lstract, was liiscusseJ. The remainder of the papers 

 on the progra lime were read and discussed. 



Mr. E. P. Rathbone's paper on "Copper-Mining in the Lake 

 Superior District " comprised a general description of the 

 district, the method pursued in mining, and the system of ore- 

 dressin,' and machinery employed. The ore employed is what 

 is known mineralogically as " native'copper." It does not occur 

 in true fissure veins, but rather in beds, or, as they are not inaptly 

 termed in the district, "belts," dipping at the same inclination 

 as the " country " or rock inclosing them. 



From exhaustive scientific investigations into the origin and 

 derivation of the copper in these deposits, it appears probable 

 that it was infiltrated into them in the form of an aqueous solu- 

 tion of copper, which also appears to have had a strong 

 chemical affinity for special constituents of the rocks, thereby 

 giving rise to a series of chemical reactions, whence resulted the 

 precipitation of native copper in a more or less concentrated 

 state, according to the proportion and the even distribution or 

 otherwise of the precipitating or displacing agent present in the 

 original rocks. In the amygdaloiJal trap-rocks the displacing 

 agent appears generally to have been less evenly distributed 

 than in the congloniei .ites ; in certain places the concentration 

 of the displacing agent has been so excessive as to give rise to 

 the form.ation of large masses of copper. Whether or not the 

 precipitating action w.as connected with some natural process of 

 lixiviation, influenced by terrestrial electrical currents, it is im- 

 possible to decide. In the amygJaloidal trap-rocks the vein- 

 stone is frequently composed largely of epidote, a mineral whose 

 presence is regarded as favourable or "kindly" to copper. 

 Other minerals found in association with the hornblendic and 

 augitic porphyries that constitute the veinstone proper, are 

 quartz, calc-spar, and many varieties of the zeolite group. The 

 commercial c 'pper sm Ited from these ores being entirely free 

 from deleterious matters, such as arsenic, bismuth, antimony, 

 &c., is especially valuable for electrical purposes, as the con- 

 ductivity of copper is reduced by the presence of foreign matter 

 even in the minutest proportions, a trace of arsenic reducing the 

 conductivity 20 per cent. In the manufacture of brass, again, 

 the presence of antimony is most deleterious : one tenth of i per 

 cent, converts first-rate "best selected" into the worst possible; 

 one-fortieth of l per cent, renders it unfit for anything but in- 

 ferior brass ; one-eightieth of i per cent, changes " best selected " 

 into "tough ingot" ; one-tenth of I per cent, of either bismuth, 

 arsenic, phosphorus, nickel, or cobalt, is sufficient to turn " best 

 selected ' into tough metal. 



There are two methods pursued: "mass mining," where 

 copper is found concentrated into masses varying in weight 

 from a few hundred i):)und3 up to many tons ; and "stamp-rock 

 mining," where the copper occurs in a more or less divi led state, 

 and usually pretty evenly disseminated throughout the whole 

 veinstone, so that its separation from the matrix organgue can be 

 economically effected only by stamping and by the subsequent 

 processes orlinarily employed in mechanical ore-dressing. The 

 more evenly the copper is distributed throughout the veinstone, 

 the more valuable is the latter, and hence it is that veinstone 

 producing only 075 per cent, can be worked profitably at the 

 present low price of copper. 



The object of ore-ilressing is to separate as far as possible the 

 small percentage of valuable metal occurring in the ore from the 

 worthless matrix or gangne, and concentrating it to the highest 

 degree of purity practicable. The mdn feature of the process 

 may be said to consist in applying to copper ore the principles 

 and the machinery already employed elsewhere in the dressing 

 of tin and le id ores. 



In the Lake Superior copper-mining the features which 

 appear to the author most worthy of special attention are : — (l) 

 The care with which the exploratory workings are kept in advance 

 of the sloping. (2) The general use of machine drills, which 

 admits of opening up the mines at a rate otherwise impracticable. 

 This is one of the few localities where drills are employed for 

 sloping, and it has been found that two or three times as much 

 rock can be sloped in the same time by drill as by hand. 

 (3) The care bestowed upon the separation of the copper from 

 the gangue by dressing. 



M. Marc lierrier-Fontaine's paper was descriptive of his 

 portable liydraulie drilling-machine, by means of which holes 

 are drilled in a single operation through all the superposed 

 thicknesses of metal without stopping the drill, which insures 

 that all the holes are quite true. By its use 25 per cent, more 

 holes are drilled than can be drilled by stationary machines in 

 the shops. 



Mr. H. Teague's notes on the pumping-engines at the 

 Lincoln Water-works, which the Institution visited at its 

 summer meeting last year, are mainly of a technical character. 

 It is interesting to learn that when in 1884 still further pump- 

 ing posver was required, the author, from experience gained at 

 Grantham, Maidstone, and other places, decided to revert to the 

 Cornish pumping-engine, as he had been convinced that the cost 

 of coals and repairs had been reduced in some instances to as- 

 low as only one-sixth of the annual expenditure pertaining to 

 rotatory pumping-engines previously in use there. 



THE SCOTTISH METEOROLOGICAL SOCIETY' 



'T'HE Journal of the Scottish Meteorological Society, which 

 -'■ has recently been published, contains, in additio 1 to copious 

 tables of the meteorology of 18S5, several papers of more than 

 usual interest. Prof. Piazzi Smyth leads with a suggestive paper 

 on hygrometric observation, based chiefly on observations made 

 by him in the neighbourhood of Malvern in the summer of 1885, 

 on fifteen successive days, at 9 a.m., in June, at a height of 

 125 feet ; and subsequently for twenty successive days at the 

 same hour but at a height of 350 feet. Scrupulous care was 

 taken to have the dry-bulb surrounded with air as nearly as possible 

 of the same quality as that of tlie free atmosphere outside, by 

 placing a large and tall black iron chimney on the top of the 

 Stevenson screen, according to Mr. Aitken's idea of promoting a 

 current inside the screen ; and to have the wet-bulb as perfect as 

 possible by enveloping it in thin muslin, tightly drawn over its 

 surface, and by securing that it w.is always thoroughly wet for 

 each oHservation. The results gave for the lower station a mean 

 depression of 3' '4 of the wet- below the dry-bulb ; and 6° '4 for 

 the upper station. It is probable that these results would be 

 found to be higher than what obtained at the three or four 

 stations in Central England nearest to Prof. Smyth's at the 

 same dates ; and without a doubt the value of the inquiry would 

 have been enhanced if such comparisons had been made and 

 recorded in the paper. 



An important point would be gained if such inquiries led 

 meteorologists more earnestly to consider the necessity of im- 

 proving the means and methods of observing and reducing the 

 observations of this most important element of the atmosphere, 

 it being by its aqueous vapour that the disturbing influences at 

 work are called into play, giving rise to winds, storms, rain, 

 snow, hail, electric displays, and other atmospheric phenomena. 



Mr. Omond, in an interesting paper on the wind and rainfall 

 of Ben Nevis in 1885, based on the hourly observations at the 

 Observatory, shows that the direction of wind with which 

 most rain fell was a little to the north of west, and that the 

 quantity diminishes round the compass in both directions from 

 this until the driest point is reached a little to the south of east : 

 east winds having a very low value. As regards the rate of fall 

 with each wind during the time it lasts, north-westerly winds are 

 the wettest and easterly and south easterly winds the driest. 

 Since south-easterly winds mostly occur when an anticyclone is 

 moving off' and a cyclone approaching, the fact of their dryness 

 at the Observatory, 4406 feet high, is a valuable contribution to 

 our knowledge of storms, since the same winds under the same 

 conditions at lower levels are notoriously wet. 



A hopeful inquiry is being carried on at the Ben Nevis Ob- 

 servatory by Mr. Rankin, first assistant, on rainband observations ;. 

 and from the results already obtained there can be little doubt 

 that when a complete low-level observatory, with hourly observa- 

 tions, has been established at Fort William, much light will be 

 thrown on the vertical distribution of vapour in this part of Great 

 Britain, and its important bearing on forecasting the weather. 

 The observations for seven months are discussed, and the means 

 show that a heavier rainband indicates with steady regularity a 

 larger rainfall as determined by the hourly observations. 



But the most important contribution of new facts in the Journal 

 are thirty-nine pages of temperature observations made on the 

 Firth and Lochs ot the Clyde from March to November 1886, by 



' Joum.il of the Scottish Meteorological Society, Third Series, No. iii. 

 (Edinburgh and London ; William Blackwood and Sons.) 



