♦ KNOWLEDGE - 



[November 1, 1886. 



until relief is required in some direction, the changes of 

 atmot'pheric pressure, iudicateJ by abnormal atmospheric 

 conditions, may be as the last feather ou the back of the 

 provei'bial camel, and may actually bring about the earth- 

 quake in the same sense that the touch of a feather on a 

 hair-trigger may bring about the explosion of the gun. But 

 the still and heavy air (as we are apt to call it, though 

 usually the barometer gives a different account of the 

 matter) tells us nothing of the state of the earth's interior. 

 It only tells us that if the earth's interior is in a state of 

 strong tension nearly balanced by resisting forces, a distui'bance 

 is very likely to follow the abnormal condition of atmospheric 

 pressure. When we remember that an alteration of two 

 inches in the height of the barometer mea'is a change of 

 half a pound in the atmospheric pressure on each square inch 

 of the earth's surface, and that often the area beneath which 

 the tensions resulting in an earthquake are at work may be 

 twenty miles square, we see that such an alteration of 

 atmospheric pressure as often precedes a great storm may 

 very well serve as tiigger-puller to the earth's imprisoned 

 forces and bring about an earthquake. In a region ten 

 miles square, there are one hundred squai'e miles, each 

 containing about three milhons of square yards, in each of 

 which are nearly thirteen hundi'ed square inches. So that 

 thei'e are not far from 400,000 millions of square inches in 

 a surface of ten miles squai-e. Thus a difi'erence of two 

 inches in the height of the mercurial bai'ometer on a 

 smface of that ai'ea would mean nearly 200,000 millions of 

 pounds', or 100 millions of tons', diflerence of atmospheric 

 pressure. This would be a mere nothing compared with 

 the tremendous jwessures which such a poitiou of the 

 earth's crust is able to sustain and resist. But regarded as 

 a change of pressure, it would be a very potent factor in a 

 nicely balanced contest between the earth's crust and the 

 reaction of inteiior strains and tensions. One may I'epresent 

 the diflerence of atmospheric pressure even more effectively ; 

 perhaps as equivalent to a flood of watei' covering the 

 whole of the one hundred square miles to a depth of moie 

 than 2;^ feet. 



As regards magnetic and electric disturbances, it may 

 suffice to mention that those observed on the present 

 occasion followed the earthquake, and that it might be 

 taken almost for granted that no gi-eat subterranean 

 distui'bances could possibly take place without electrical 

 and magnetical phenomena of an unusual kind being 

 observed. To imagine, as some have done, that a mag- 

 netical storm, even if it had chanced to precede an earth- 

 quake, could have brought the earthquake about, is almost 

 as preposterous as that blunder which set the scientific 

 world on the broad grin nearly a quarter of a century 

 ago, when it was gravely suggested that the Great Eastern, 

 then missing, might have gone down in the great magnetic 

 storm announced at tJreeuwich ! 



The earthquake of August 31 was felt at Charleston at 

 0.55 P.M. It has been stated since that the wave of disturb- 

 ani« travelled from this region of greatest distui'bance in all 

 directions. But, as a matter of fact, the shock was felt 

 earlier in places at a distiince. I have before me the leading 

 St. Louis paper for September 1, in which, in an article 

 written before the news from Charleston had been received, 

 the times recorded at various stations are indicated thus : — 

 At St. Louis, 8.20 ; at Indianapolis, 8.52 ; at Na.shville, 

 8.54 ; at New York, 8.57 ; at Detroit, 9 ; at Louisville, 

 9.13 ; at Cincinnati, 9.16 ; at Cleveland, 9.38; at Atlanta, 

 9.50 ; at Washington, 9.55. (The remark is added, reading 

 strangely and .sadly in the light of the news which arrived 

 but a few hours later : " As has been usual with such 

 phenomena in the United States, very little damage to pro- 

 perty was done, and there was no loss of life.") It is barely 



possible, however, that in reality the shock thus timed was 

 felt earlier in Charleston. For the hour mentioned above 

 was not actually I'ecorded. The people at Charleston were 

 naturally little disposed to make time records when their 

 lives seemed appallingly endangered. No telegraphic news 

 of the disaster was sent out that night, insomuch that it was 

 not until the morning of September 2 that the greater part 

 of the States heard of the terrible effects of the shock in 

 Charleston. The record by which the time of the chief 

 shock was inferred was simply the clock of St. Michael's 

 Church, which had stopped at 9.55 p.m. 



COAL. 



By W. Mattieu Williams. 



N my last I described the usual methods of 

 proving coal by boring, and some of the sources 

 of peril to investors in new ventures. Also 

 the reasons why the deepest part of the seam 

 to be worked is chosen for sinking the pits. I 

 should add that where the coal is near the 

 surface, and the depth of the shafts is con- 

 sequently small, a larger number of pits are sunk on a 

 given area of laud than where the coal exists at greater 

 depths. The reason of this is simple enough. The sinking 

 of shafts is costly, and the cost of course increases with the 

 depth. Also the bringing of the coal from long distances 

 under-ground to the bottom of the shaft costs more than short 

 distances. Besides this, the woik of ventilation becomes 

 more and more comi)lex the greater the area that is worked 

 from one pair of pits. Thus the question of whether a given 

 pair of pits shall continue to be used for winning larger 

 and larger areas, or whether these shall be abandoned and a 

 new pair sunk, is answered by calculating whether the saving 

 that may be effected by shorter underground roads is sufficient 

 to cover the interest on the capital required for the new pits. 

 The great ten-yard seam of the " Black Country " between 

 Birmingham and Wolverhampton affords an example of 

 numerous pits in proportion to ai'ea. This may be noted 

 in passing thiough by rail. The pits there are not only 

 numerous, but about the most jnimitive in the kingdom as 

 regards all then- appliances. 



At Sandwell Park, near Birmingham, where, after many 

 vicissitudes of hope and fear and serious specidations, risings 

 and fallings of shares, a much deeper seam has at last been 

 reached, a remarkable contrast may be observed. 



The unsophisticated reader may wonder why I have in 

 the above only spoken of pits, or a pair of pits or shafts, 

 never of a pit or shaft in the singular. The reason is that 

 a single jnt or sh.oft is now illegal in this country. The 

 Corsicau butcher called us a nation of shopkeepeis, and 

 ignorant outsiders still believe that we, as a nation, sacrifice 

 everything to the exigencies of trade and commerce, but 

 those who choose to inquire and learn the truth will dis- 

 cover that when laws are demanded in which the claims of 

 humanity come in collision with those of profit, British 

 legislation provides for the former at the expense of the 

 latter to an extent unparalleled by the legislation of any 

 other country in the world, either ancient or modern. 

 Our factory acts for the protection of women and 

 children, and the machinery of factory inspectors to enforce 

 those acts; our laws for the compensation of injured work- 

 men, our severe enforcement of compensation for personal 

 uijuries on railways, our regulations concerning the loading 

 of .ships and the general protection of sailors, our prohibition 

 of chimney-sweeping boys, our laws agaiu.st using dogs as 

 draught animals, our legislation prohibiting female labour 

 and regulating boy labour in coal-pits, are far more stringent 



