July 27, 1882] 



NA TURE 



299 



been trying to discover some other method of arriving at 

 the same end without producing flame. 



Amongst these may be mentioned in this place : — 



1. Improvements in wedging processes. A long iron 

 wedge, placed in a previously drilled bore-hole between 

 two strips of iron with flat faces and convex backs, is 

 forced inwards by means of a screw or by hydraulic 

 pressure. 



2. Improvements in blasting processes, (a A gun- 

 powder cartridge is placed in an ordinary bore-hole, but 

 a cylinder filled with water occupies most of the remainder 

 of the hole instead of the usual tamping of rubbish 

 (HacNab's Patent). (/>) A dynamite cartridge inclosed 

 in a waterproof bag is placed in the interior of the water 

 cylinder of the last case (Abel's modification). 



(The writer conducted a long series of experiments 

 with d\namite water-cartridges for Prof. Abel and the 

 Commissioners on Accidents in Mines, and the results 

 will doubtless be published for the benefit of other inves- 

 tigators. In these experiments the mouth of the shot- 

 hole was always situated in the centre of one side of a 

 cubical bag containing 64 cubic feet of explosive gas.) 



3. The caustic lime process, which forms the principal 

 subject of the present note. 



Although the proposal to employ caustic lime in this 

 manner is not quite new, its first successful application 

 has been made by Messrs. Smith and Moore, at Shipley 

 Collieries in Derbyshire, where, thanks to the courtesy of 

 these gentlemen, we lately saw it in operation under the 

 superintendence of one of them. The seam of coal which 

 is known as the Derbyshire Deep Hard, consists of three 

 beds in immediate contact with each other. The top bed 

 — one foot thick — is of inferior quality, and is left for a 

 roof and permanently lost. The middle bed — 2 feet to 

 inches thick — produces good marketable coal in large 

 blocks, and constitutes the object of working. The 

 bottom bed — 7 inches thick — together with a bed of soft 

 shale 10 inches thick, serves as a holing. The method of 

 working is longwall— the faces being straight, and each 

 about 100 yards long. The holing is carried in to a depth 

 of about 3i or 4 feet under the roal ; and while it is being 

 done, the front of the mass which it is intended to detach 

 is supported upon short timber props (sprags) placed at 

 distances of six feet apart. 



After the holing is completed a series of horizontal holes 

 three inches in diameter are drilled close to the roof to a 

 depth of three feet or so. These holes are also about six 

 feet apart. Seven cylindrical blocks of caustic lime, each 

 2i inches in diameter by 4j inches long are placed in 

 each hole. They are prepared by grinding burnt lime to 

 a powder, and then compressing it into blocks of the 

 required shape and dimensions under a hydraulic press. 

 They are, naturally, kept and carried in airtight boxes. 

 There is a groove in each blcck parallel with its axis, and 

 large enough to receive a pipe A inch in diameter. The 

 grooves are kept uppermost in the bore-hole. An iron 

 pipe i inch in diameter, a few inches longer than the 

 length of the hole, provided with a stop-cock at its outer 

 end, and with a cloth bag drawn over its inner end, is 

 inserted into the groove of the first block and then forms 

 a guide for the others. Outside the last block the hole 

 is firmly tamped first with paper, and then with rubbish. 



After all the holes have been charged, a quantity of 

 water, said to be equal in bulk to that of the caustic lime 

 already occupying the hole, is forced into each in succes- 

 sion through the iron pipe. This is done by means of a 

 hand-pump attached to a bucket, and provided with a 

 short length of flexible hose. The stopcock of each pipe 

 is immediately closed after the water has been introduced. 

 This operation occupies about one minute for each hoie, 

 and the two men who carry it out pass along the face 

 from one end to the other. 



A sound as of steam escaping under a high pressure is 

 now heard, and here and there the tamping is blown out. 



Then follows the well-known sound of what is technically 

 called " working " while the coal is being separated from 

 the upper bed by the pressure of the expanding lime. 

 After the lapse of a few minutes it is found that the whole 

 mass of coal is resting upon the sprags, and these have 

 only to be knocked out in order that it may fall in the face. 



The time required for the various operations may be 

 divided as follows : — Drilling, 12 minutes ; charging, 4 

 minutes ; introducing water, 1 minute ; total, 17 minutes 

 for each bore-hole. 



Although this system is undoubtedly successful in the 

 circumstances under which it has been applied, it would 

 be a mistake to assume that it is likely to have anything 

 but a limited application. For it has been found by 

 experiment to be incapable of breaking down a hard rock 

 or shale roof, such as is to be met with in many mines in 

 which blasting is required for that purpose, and for that 

 alone. 



Let us take the case of Risca Colliery, so notorious for 

 great explosions, in which the roof of the roadways 

 requires to be ripped down in order to get sufficient 

 height for haulage purposes. The last great explosion 

 took place at the beginning of the present year : but, as 

 only the four men who were underground at the time 

 were killed, it passed almost without remark. Neverthe- 

 less, the damage done by it was immense ; coal-getting 

 operations had to be suspended for over a month, and 

 one large district of workings was entirely wrecked and 

 was permanently abandoned. 



And what were the circumstances under which all thi 

 took place ? Four men were firing four shots in the prin- 

 cipal intake air-way in the presence of dry coal-dust. 

 One of these shots blew out its tamping. The men were 

 all found in the intake air-way with their safety-lamps 

 uninjured. 



This is a case which the objectors to the coal-dust 

 theory both in this country and abroad would do well to 

 ponder carefully. William Galloway 



THE COLOURS Of FLOWERS, AS ILLUS- 

 TRATED BY THE BRITISH FLORA 

 I. 

 General Law of Progressive Modification 



PETALS are in all probability originally enhrged and 

 flattened stamens, which have been set apart for 

 the special work of attracting insects. It seeins likely 

 that all flowers at first consisted of the central organs 

 alone— that is to say, of a pistil, which contains the ovary 

 with its embryo seeds ; and of a few stamens, which pro- 

 duce the pollen. But in those plants which took to ferti- 

 lisation by means of insects — or, one ought rather to say, 

 in those plants which insects took to visiting for the sake 

 of their honey or pollen, and so unconsciously fertilising — 

 the flowers soon began to proiuce an outer row of barren 

 and specialised stamens, adapted by their size and colour 

 for attracting the fertilising insects ; and these barren 

 and specialised stamens are what we commonly call petals. 

 As the stamens of almost all flowers, certainly of all tre 

 oldest and simplest flowers, are ye. low, it would seem 

 naturally to follow that the earliest petals would be yellow 

 too. When the stamens of the outer row were flattened 

 and broadened into petals, there would bs no particular 

 reason why they should change their colour ; and, in the 

 absence of any good reason, they doubtless retained it as 

 before. Indeed, the earliest and simplest types of existing 

 flowers are almost always yellow, seldom white, and never 

 blue ; and this in itself would be sufficient ground for 

 believing that yellow was the original colour of all petals. 

 But as it is somewhat heretical to believe, contrary to 

 the general run of existing scientific opinion, that petals 

 are derived from flattened stamens, instead of from sim- 

 plified and attenuated leaves, it may be well to detail here 



