April 30, 1908J 



NA TURE 



619 



meter had become crusted with ice spicules, and it had 

 to be thawed out before it could be used. Many other 

 difficulties had to be encountered, and it is surprising that 

 any successful observations were made ; but Mr. Mossman, 

 assisted by Mr. W. Martin, secured, besides other observa- 

 tions, hourly observations on twenty days. 



The magnetic observations are discussed by Dr. Chree, 

 F.R.S., who remarks that the results show how very 

 carefully the observations were made. The observations 

 extended over the period May, 1903, to February, 1904. 



The following values are given : — declination, 5° 3i'2 

 cast; inclination, 54° 3o'-6 south; horizontal force, 0-25704; 

 mean daily range of declination obtained from the hourly 

 readings, S'-65. 



While the Scotia was anchored and frozen in Scotia 

 Bay observations of the tide were made by means of a 

 very simple gauge. A long wire, fastened to the sea floor 

 by a heavy weight, passed over a pulley, and was kept 

 taut by a lighter weight at the other end. As the ship 

 rose and fell with the tide this weight moved up and down 

 a vertical scale, which was observed half-hourly. 



The tides seem to be normal for a place in the Southern 

 Ocean. The semi-diurnal tides are considerable, but the 

 solar tide is unusually large compared with the lunar tide, 

 the ratio being three-fiftlis, or 0-6, as compared with 0'465 

 of the equilibrium theory. The semi-diurnal tides are 

 almost exactly " inverted," so that low water occurs very 

 nearly when the moon is on the meridian. 



THE METEORS OF HALLEY'S COMET. 

 TX view of the approaching return of Halley's comet, the 

 ■'■ Aquarid meteor shower of May ought to bo awaited 

 with special interest. We know comparatively little of 

 this system, as it has been seldom observed. It is certain, 

 however, that it is the richest of our May showers, and 

 that its radiant point conforms very nearly both in date 

 and place with the radiant and epoch of particles follow- 

 ing the path of Halley's comet. This circumstance alone 

 is significant, and the supposed connection of the comet 

 and meteoric display will be sure to receive ample investi- 

 gation during the next few years. 



The Aquarids should be looked for after V a.m. in the 

 mornings between the end of April and May 7, and they 

 are directed from a region at about 337° — 2°, just below 

 the equator. Lieut. -Colonel Tupman determined the 

 radiant as about 10° west of the point assigned, and 

 further observations are required to ascertain the exact 

 place, and also the precise date of the maximum of the 

 shower. 



If really associated with Halley's comet, the meteors 

 ought, in immediate ensuing years, greatly to increase in 

 numbers, though we possess no historical records of rich 

 showers having been observed in 1759 or 1835, when the 

 comet previously returned to perihelion. But many 

 meteoric phenomena have eluded recognition, and it is very 

 possible that some returns of these Spring ,'\quarids may 

 have escaped notice, as they are only visible just before 

 sunrise, and were never specially looked for until after 

 their discovery nearly forty years ago by Lieut. -Colonel 

 Tupman. This stream, like the Perseids and Leonids and 

 many other showers, is evidently one visible nearly every 

 year! and forming a complete ellipse. It now remains for 

 observations in immediately ensuing years to determine 

 whether, like the Leonids and Andromedids of November, 

 it develops unusual intensity near the time of return of 

 the parent comet. W. F. Denning. 



SOME UNSOLVED PROBLEMS LV METAL- 

 MINING.'- 

 TX one sense every mine is an unsolved problem from 

 •'■ the day the first pick is put into the ground until the 

 mine is finally abandoned as exhausted, and even then it 

 is not always certain that it really is worked out, and that 

 sinking or driving another 10 feet might not give it a 

 renewed lease of life. Unlike most engineering problems, 

 which have generally to be solved before work is com- 



1 From the "James Forrest" Lecture, delivered at the Institution of 

 Civil Engineers on .April 27 by Prof. Henry Louis. 



NO. 2C0Q, A"OL. 77] 



menced, a mining problem is never fully solved until all 

 work upon it is finally concluded. 



At the very outset, even before we are in a position to 

 attaclc the different subdivisions of the subject, we are 

 brought face to face with what may almost be described 

 as one of the fundamental problems underlying the whole 

 of metal-mining, and one the solution of which can never 

 attain finality. The work of the metal-miner being limited 

 to the extraction from the earth's crust of the ores of the 

 various metals, whilst it is the business of the metallurgist 

 to smelt these, so as to reduce therefrom the metals that 

 they contain, and to fit the latter for their use in the arts, 

 the question what constitutes an ore is one that the miner 

 cannot answer for himself, and for the reply to which he 

 is dependent entirely upon the development of metallurgical 

 science for the time being. Xot all metalliferous minerals 

 are ores from the smelter's point of view. Take, for 

 example, an ordinary brick clay, which is a complex 

 hydrous silicate containing, say, 15 per cent, of aluminium 

 and 5 per cent, of iron ; it is true that we can extract 

 both these metals from it by a series of complicated labora- 

 tory processes, but no means for doing this economically 

 on a practical working scale have yet been discovered. 

 Hence no one would dream of calling clay an ore of 

 aluminium, and far less of iron. Nevertheless, it is not 

 beyond the bounds of possibility that our modern metal- 

 lurgists, or their younger and more progressive brethren, 

 the electro-metallurgists, may within a few years devise 

 some practicable process for extracting aluminium from 

 clay, when clay would straightway become an ore of 

 aluminium, though it is not one now ; and if perchance 

 it happened that comparatively pure oxide of iron were 

 obtained as a by-product in the same process, the clay 

 might even be reckoned as an ore of iron also. Until 

 some such process shall be devised, clay is looked upon 

 by the metal-miner as a non-metallic mineral, as so much 

 worthless gangue or w^aste. The history of metal-mining 

 has shown again and again that the waste rock of one 

 generation is the valuable ore of another, as, for example, 

 the zinc blende of the Alston district, which is now being 

 recovered from the waste which the old miners had left 

 behind as worthless in their excavations, or had thrown 

 aside on their waste heaps, the value of the mineral having 

 been recognised when a Belgian metallurgist discovered 

 how to extract zinc from it. 



The point may be further illustrated by a consideration 

 of the world's supply of iron ore; iron, the most useful 

 of all metals, is at the same time, next to aluminium, the 

 most abundant, geologists calculating that 47 per cent, of 

 the earth's crust consists of iron; if this estimate be 

 correct, the very small portion of the earth's crust under- 

 lying the London Metropolitan area (fifteen miles' radius) 

 down to the depth of only one mile would contain no less 

 than 360,000 millions of tons of iron, none of which is in 

 the form of a true iron ore. .'\t the present day no one 

 would call a mineral containing less than 25 per cent, of 

 iron an iron ore, and unless it contains double that per- 

 centage it will not find a very ready or a very appreciative 

 market amongst iron smelters. 



As the result of various improvements in the last few 

 decades, the whole trend of modern mining is towards the 

 utilisation of large deposits of low-grade material, the 

 increased scale of operations enabling economies to be 

 effected that were impossible whilst small quantities alone 

 were dealt with. One of the cardinal problems that will 

 confront our successors will be how to work with profit 

 minerals of lower grade than any that we have yet 

 attacked, so as to enable the miner to include within his 

 sphere of operations deposits too poor for us to deal with 

 to-dav. 



The possibility of determining by some means the where- 

 abouts of the hidden treasures of the earth has long been 

 an object of the miner's desire, the methods for accomplish- 

 ing which range from the inedi.-Eval adept with his divining 

 rod, belief in which is not wholly extinct to-day, down to 

 a series of modern attempts to use electric currents for 

 the same purpose. Up to the present these atteinpts have 

 been unsuccessful, in spite of the ambitious claims of some 

 of their advocates. 



In view of the fact that minerals differ so widely_ ifi 

 their electric and magnetic properties, it is quite possible 



