April 16, 1886.] 



SCIENCE. 



34T 



In order to obtain clear and convincing results 

 in the investigations under discussion, a long 

 series of analyses of the air from the well and 

 regularly ventilated mine was made at the same 

 time that barometric observations were taken. 

 For the latter purpose a barograph was placed in 

 the lowest part of the mine, at a depth of 230 

 metres, and the close correspondence between the 

 changes of pressure at the surface and in the mine 

 was ascertained. There a large number of daily 

 analyses were made of the air taken from the 

 ventilator, and also of air taken from a level in the 

 seam by an independent apparatus. 



These experiments were commenced in the be- 

 ginning of June,. 1885, and are still going on. The 

 first report published by the archducal finance 

 director in Teschen, based on the experiments 

 made from June 5 to July 13, shows, that, when 

 the barometer fell, the proportion of explosive gas 

 in the ventilator and mine increased. The later 

 experiments confirm this result in the most strik- 

 ing manner. The report referred to expresses the 

 results of the early experiments as follows : — 



1. The proportion of explosive gas in the mine 

 air, generally speaking, decreases with increasing 

 atmospheric pressure, and increases with a decreas- 

 ing pressure. 



2. The proportion of gas increases more rapidly 

 the more suddenly the barometric curve falls, and 

 decreases more rapidly the more suddenly the 

 curve rises. 



3. The development of the gas does not depend 

 on the absolute amount of barometric depression. 



4. If the barometric curve ascends at first sud- 

 denly and then slowly, or remains stationary for 

 some time after reaching a maximum, a slow in- 

 crease of gas is observed. If, after a sudden fall 

 of the barometer, the pressure continues to de- 

 crease slowly, or remains stationary some time 

 after reaching a minimum, a slow decrease of gas 

 is observed. The maximum and minimum of the 

 barometric curve, therefore, do not always cor- 

 respond to the minimum and maximum of the 

 gas curve. 



Not content with these observations, a further 

 series of experiments was undertaken. Work on 

 the mine was stopped, and the air-supply shaft 

 was closed while the ventilator was kept running, 

 This experiment was begun at noon on June 20, 

 and continued twenty-seven hours. In order to 

 obtain the usual number of revolutions of the 

 ventilator, the steam-pressure had to be increased. 

 The barometric pressure in the mine sank 2.2 mil- 

 limetres in five minutes, while the proportion of 

 gas at the ventilator (which was ventilating other 

 workings at the same time) rose to 0.83 per cent, 

 and, at the level where separate collection was 



made, to about 0.40 per cent. In subsequent ex- 

 periments a barometric depression of 4 millimetres 

 was reached in the mine, the ventilator stopped, 

 and in one case the gas in the level reached 1.35 

 per cent. This artificial depression of from 2.2 

 millimetres to 4 millimetres is certainly small in 

 comparison with the natural variations in atmos- 

 pheric pressure which are going on all the time, 

 but its sudden production accelerated proportion- 

 ally the flow of gas in the mine. Of the five 

 severest accidents in coal-mines which have hap- 

 pened recently, four occurred during periods of 

 especially low barometer. The accident at Polish 

 Ostran on the 8th of October, 1884, occurred when 

 the barometer sank 11 millimetres in forty-eight 

 hours. The explosion at Karwin on March 6, 

 1885, took place on the second day of the fall of 

 the barometer, which lasted three days and 

 amounted to 16 millimetres. That at Saar- 

 briicken occurred also on the second day of a fall 

 of about 13 millimetres ; and that at Clifton Hall 

 on June 18, 1885, took place at the beginning of a 

 fall. The accident at Dombran on March 7, 1885, 

 is generally attributed to coal-dust. To these five 

 accidents must now be added that at Spekul in 

 Banat, which took place at nine o'clock in the 

 morning of Oct. 29, 1885. In the absence of more 

 accurate data, it may be remarked that on the 

 28th of October the barometer was 754.2 milli- 

 metres at seven in the morning, at Hermannstadt ; 

 on the 29th it was 750.6 millimetres, and on the 

 30th 749.8 millimetres. 



It is superfluous to enlarge upon the experiments 

 at Karwin. They confirm the views of the English 

 experts and those expressed by Cowen before the 

 English parliament in 1878, and it may be pre- 

 sumed that they will produce a change of opinion 

 in other countries where those views are not 

 known. They show the great importance of the 

 barometer in coal-mining. The isobar-charts, 

 which are obtaining a wider publication every 

 year, show the daily progress of barometric min- 

 ima over Europe, and they should be consulted in 

 future by the managers of every coal-mine. The 

 order is already in force at Karwin, forbidding 

 blasting at all dangerous points on the approach 

 of a barometric depression, and, if the danger 

 increases, all work is to be suspended. M. 



NOTES AND NEWS. 



Dr. Palisa of Vienna detected still another 

 small planet, April 5 : it was of the thirteenth 

 magnitude, and will bring the total number of 

 these bodies up to 257. 



— The national museum has received a fine speci- 



