52« 



NA TURE 



[September 19, 1907 



ii.ir.cs; to-dav, after many experiinpnts with rompresscd 

 powder, cotton-powder, and other such compounds, and 

 after nitro-glvccrin had been tried and given up because 

 of its danger, only such " high explosives " as dynamite, 

 gelignite, and the like are used. These high explosives 

 onlv came into use after much experimenting, by the Royal 

 Cornwall Polytechnic Society in particular, but they have 

 proved themselves very serviceable, especially in hard 

 giound, and they are also found to be much safer in use 

 than the old black powder. 



Great improvements have been efTected in the machines 

 used for compressing the air employed in working the 

 machine-drills; compound engines, compressing the air in 

 successive stages, are now generally employed in the larger 

 mines. 



Compound engines, mostly of the tandem type, were 

 introduced into several Cornish mines by Mr. Sims more 

 than half a century ago, but with the low-pressure steam 

 then employed did not recommend themselves, and so went 

 out of use.' A compound engine using high-pressure steam 

 has been employed for years past in pumping at the Basset 

 Mines for working the ordinary force pumps ; of late many 

 attempts have been made to introduce centrifugal pumps 

 operated by electricity for draining the mines. A certain 

 measure of success has attended these efforts, particularly 

 at the Tywarnhaile Mines, and more recently at Wheal 

 Vor ; but it must be admitted that up to the present the 

 Cornish system of pumping, the rods being operated by a 

 simple vertical engine, single acting in the case of large 

 installations, holds the field. 



The use of electricity is spreading in the Cornish mines 

 apart from pumping. At East Pool it has long been 

 employed for surface traction, the mill being a mile or 

 more awav from the mine. At South Crofty it is employed 

 for operating the new stamp mill ; in several mines it 

 supplies power to work pulverisers, buddies, and other 

 dressing machines, and in this direction — as also in electric 

 lighting — there is a large field for extension. 



There have been great improvements in the engines used 

 foi- winding during the past few years. It no longer takes 

 thirty to forty minutes to raise a kibble of stuff from the 

 bottom of the deeper mines, as it did at one time ; skips 

 running between guides are now common, cages bringing 

 the ore-wagons direct to surface are employed in several 

 mines, while the men are mostly brought up from below 

 in shaft-gigs or special skips, so that the man-engine, once 

 so great a booh and used in ho fewer than twelve mines, 

 can now only be seen in operation in the Levant Mine. 

 For modern winding wire-ropes are universally used, and 

 are practically indispensable. Accidents from its use arc, 

 indeed, exceedingly rare. Mr. Morgan's traversing engine, 

 erected some years since for hoisting from Williams's 

 Shaft at Dolcoath, will soon be at work again, but so far 

 no proposals seem to have been made for using this re- 

 markable engine anywhere else. 



For signalling in shafts the old " knocker line " is still in 

 use, and has its advantages. Indicators for the guidance 

 of the engine-man are. of course, placed in the engine 

 house in every case where men are raised, and in most 

 other cases; overwinding is an. extremely rare occurrence, 

 such is the carefulness of the engine-man. The telephone 

 was introduced in Wheal Eliza, bv Dr. Le Neve Foster 

 many years ago for signalling from below, but it did not 

 " catch on." It is, of course, used for ordinary business 

 purposes in several of the mines. 



The steam-boilers used in Cornwall are mostly of the 

 Cornish or Lancashire type, and work at comparatively 

 low pressures. The number of these boilers working above 

 6olb. . is not very great, and those working at loo of 

 more could almost be counted on the fingers. Multitubular 

 boilers, portable or semi-portable, are used in some in- 

 stances where good water is obtainable, and particularly 

 for winding, while the electrical pumping plant at Tywarn- 

 haile is worked by engines which consume "suction gas." 

 Many improvements have been introduced in the treat- 

 ment of ores: the ores treated in Cornwall now are almost 

 exclusively of tin, copper ore being rare, while the working 

 of iron, lead, and zinc ores has practically ceased. 



The first crushing is generally done by stonebreakers of 

 the Blake type, followed by stamps of the Cornish, Cali- 

 fornia, or pneumatic type, the " rows " being finally 



reduced by some form of pulveriser. Self-feeders have 

 not yet been used for the Cornish stamps, but they arc 

 always employed in connection with the California and 

 pneumatic stamps. At Dolcoath powerful batteries of all 

 three types can be seen regularly at work. 



For dressing the crushed ore, while buddies are still very 

 generally used at some stages, Wilfley, Buss, or other 

 tables of the percussion type, or Fruc vanners are em- 

 ployed in most of the larger mines. Hydraulic separators 

 are mostly used to remove the slimes before feeding the 

 pulp to the Wilfley and Buss tables, but in the case of the 

 Frue vanner the slimes are generally removed for separate 

 treatment at a later stage. 



For slime treatment there is still nothing better known 

 than the dead-frame, the ordinary round slime table, or 

 the Acme table. The old-fashioned swinging rack for 

 cleaning slime has practically disappeared, though it had 

 soine notable merits. 



Most tin-ores need calcination before they can be cleaned 

 for the market. In some of the smaller mines the old 

 reverberatory oven is still in use, but in the larger mines 

 the Brunton revolving calciner is always employed. 



The calcination of tin-ores yields in some mines large 

 quantities of " ;irsenic-soot," which is collected in long 

 flues of masonry ; this soot, at one time valueless or worse, 

 is now an important by-product. It is handled by the 

 ton as freely as sand, and apparently with equal impunity 

 for cases of arsenic poisoning are far rarer in Cornwall 

 than in London. Another important by-product in some 

 mines is wolfram, which at one time was merely a 

 deleterious component of the dressed tin, but is now profit- 

 ably extracted at many of the inines, and in particular at 

 cutters United, East Pool, and South Crofty by means of 

 the WetheriU magnetic separator. In this machine the 

 powdered and thoroughly dried concentrates are carried 

 slowly over electro-magnets on traversing belts. The 

 magnets remove the slightly magnetic particles of wolfram, 

 while the non-magnetic particles of cassiteritc pass on and 

 fall into a separate receptacle. The wolfram so separated 

 in most cases still contains a considerable percentage of 

 tin-oxide. At the mines mentioned this tin-wolfram pro- 

 duct is " pickled " with dilute acid (aided by jets of steam 

 at East Pool) in order to remove certain highly magnetic 

 iron oxide components, which seriously interfere with the 

 operation of the magnetic separator. A similar " pickling " 

 was recommended by Dr. Richard Pearce forty years ago, 

 and has occasionally been used for the removal of copper 

 from calcined tin ores. 



At Tynwarnhaile, and also at Dolcoath, the Elmore oil 

 processes have been, or are being, introduced for the con- 

 centration of low-grade copper ores. The wet ore-pulp is 

 mixed with oil and subjected to a partial vacuum, by 

 which means the ore-particles are floated up from the waste 

 as a sort of mineral scum, which is readily separated from 

 the waste, and with much less loss than is the case by the 

 methods hitherto employed. 



Enough has been said in this hasty summary to show 

 that tne Cornish miner to-day, as in the past, is very ready 

 to avail himself of such new methods and appliances as 

 have a reasonable prospect of success, although it must be 

 admitted that he is rather fond of letting other people 

 experiment for his benefit. J. H. Collins. 



NO. 1977, VOL. 76] 



THE IRISH PEAT INDUSTRIES.^ 



A CCORDING to reports published in 1814 by the Bog 

 -'"^ Commissioners, Ireland possesses 3,028,000 acres of 

 "peat bog," of which 1,648,000 acres form "available" 

 or so-called " red " bog, and about 1,380,000 acres form 

 " mountain peat soil." The " red bog " is mainly con- 

 fined to the great central plain of the island, and the 

 " mountain bog " to the counties of Wicklow, Donegal, 

 Mavo, Galway, and Kerry. As the accompanying outline 

 bog map (Fig. i) shows, there are few portions of the 

 island destitute of bog. 



The slow but continuous reclamation of Irish bogs 

 which has been going on for the past three hundred 

 years is referred to in a work written, in 1645, by Dr. 



t Abridged from ttie Economic Frjceedings cf the Royal Dublin Society, 

 vol. i., part x. (July) » 



