May 6, 1887.] 



SCIENCE. 



429 



consequence, year follows year, and the very sen- 

 sible recommendation is unheeded. It is esti- 

 mated by a naval officer who has given a great 

 deal of attention to this subject that the actual 

 annual loss to the merchant marine of the United 

 States from striking upon these unmarked ob- 

 structions is equal to at least ten per cent of the 

 losses from all other causes combined. The cost 

 of building and maintaining the necessary vessel 

 to remove these obstructions vpould be more than 

 saved in the first year by the prevention of losses 

 to coasting-vessels and transatlantic steamers 

 which are jeopardized by the failure of the gov- 

 ernment to do its duty in this respect. 



EXPLOSIONS IN COAL-MINES. 



'A REPORT by W. N. and J. B. Atkinson, in- 

 spectors of coal-mines for the north of England,' 

 recently published, is a very valuable contribution 

 to our knowledge of an intensely practical sub- 

 ject, viz., the causes of explosions in coal-mines ; 

 and it is simply wonderful, considering how much 

 this question has been investigated during the last 

 hundred years, that some of the most important 

 facts should not have been correctly apprehended 

 or fully appreciated until this late day. 



The nature of one cause of explosions, fire- 

 damp or coal-gas, was demonstrated long ago, 

 and guarded against by the invention of the 

 safety-lamp. But that there must be some other 

 cause at least equally potent has long been evi- 

 dent to thoughtful minds, from the fact, that, 

 where the safety-lamp is in general use, explosions 

 are still distressingly frequent and fatal. Thus 

 official statistics for the years 1850 to 1885 show, 

 in the United Kingdom alone, an annual average 

 of fifty-six fatal explosions, the annual loss of 

 Kfe for the same period averaging two hundred 

 and thirty-seven. 



The report of the Messrs. Atkinson shows that 

 the dust in coal-mines is now the chief explosive 

 substance, the explosions usually resembling those 

 in the large fiouring-raills of Minnesota. This is 

 not a hasty or foregone conclusion on the part of 

 the authors, but it has a broad basis of experience 

 gained by the direct and careful investigation of 

 many important explosions. The discussion is 

 able and thoroughly scientific, for not only is 

 every statement abundantly fortified with facts, 

 but it is made very clear in every case that no 

 other view is tenable. 



In all the collieries of the north of England the 

 coal-seams lie at a considerable depth below the 

 surface, with which they are connected by at 

 least two shafts, — a downcast for the admission 



of fresh air, and an upcast for the escape of the 

 foul air from the workings. The circulation is 

 Tisually maintained by a furnace at the bottom of 

 the upcast shaft. The fresh air passes from the 

 downcast by straight roads, from which lateral 

 escape or leakage is prevented, to the working 

 faces, and thence returns by other roads and 

 through the abandoned parts of the colliery, 

 where the coal has been removed and the roof al- 

 lowed to fall in, to the upcast. The intake air- 

 ways are usually the oldest parts of the workings, 

 and are also the main avenues for hauling out the 

 coal and for the ingress and egress of men and 

 horses; while the return airways are rarely used 

 for any other purpose than the passage of the foul 

 air. 



Fire-damp or light carburetted hydrogen exists 

 in all the coal of this district, and issues con- 

 stantly from the freshly exposed surfaces in the 

 working places : but the ventilation is usually so 

 efficient, that the gas cannot be detected even 

 along the return airways, and it is very rarely ob- 

 served on the main intake roads traversed by 

 large volumes of fresh air, their surfaces having 

 long exhausted themselves of gas. Naked lights 

 are often used in the outer portions of the intake 

 roads, and locked safety-lamps, as a rule, in all 

 other parts of the colliery. Observations are 

 cited which show, that, while one volume of fire- 

 damp to fifteen volumes of air is required to make 

 an explosive mixture, in the first half-mile of the 

 intake roads the proportion cannot exceed one 

 volume of fire-damp in fifteen hundred volumes 

 of air. And yet it is exactly in this part of the 

 colliery that the explosions are most frequent and 

 violent. 



The coal is largely of a tender or dusty nature ; 

 and, although the shafts are usually wet, the work- 

 ing planes are, for the most part, quite dry, and 

 the air especially, although moistened by its pas- 

 sage down the wet shaft, becomes very dry 

 through the rise of temperature due to the fact 

 that the temperature of the ground increases 

 downwards. 



The return airways, where the fire-damp is 

 most abundant, are usually quite free from dust, 

 and at the working faces the dust is not often a 

 sei'ious evil. But the principal accumulations of 

 dust are found along the roads through which the 

 coal is hauled, i.e., the intake airways. It is es- 

 pecially abundant where the coal is hauled by 

 engine-power, or at a high rate of speed. The dust 

 is shaken and blown out of the cars by their rapid 

 motion against strong currents of air, and flies 

 as a cloud along the top of the train. The heavier 

 particles fall to the bottom of the roadway, and 

 the lighter particles form a deposit on the upper 



