390 



SCIENCE. 



[Vol. VII., No. 169 



and in the return air-ways. It has been demon- 

 strated in our experiments, that, when the atmos- 

 phere contains five to five and one-half per cent 

 of marsh-gas, it becomes highly explosive. We 

 have even obtained explosions which, though less 

 violent, might be nevertheless destructive of life 

 if they occurred, on the large scale possible in a 

 mine, when the air contained only four per cent 

 of marsh-gas. It will thus be seen that air which 

 would appear free from gas if tested in the ordi- 

 nary way, may become, by the addition of only 

 about two per cent of marsh -gas, capable of 

 propagating flame and causing destruction, while 

 the addition of about three per cent converts it 

 into a highly explosive mixture. Air which 

 would appear quite free from gas if examined by 

 a lamp-flame, may become explosive when laden 

 with fine, dry coal-dust. Appliances now exist 

 by which very small proportions of marsh-gas 

 in air may be readily detected, and which can be 

 used for examining the atmosphere of a mine. 

 With Liveing's indicator, gas present in the air 

 can be estimated with sufficient accuracy for all 

 practical purposes, even when the proportion is as 

 low as one-quarter per cent." 



In connection with this subject, the suggestion, 

 first due to Mr. Galloway, that coal-dust alone 

 suspended in air might cause an explosion, is con- 

 sidered, and an account is given of some care- 

 fully devised experiments which rather tend to 

 confirm this conclusion. The commissioners dis- 

 cuss with some detail the means of removing this 

 dust, and devote a large section of the report to 

 the question of the conditions under which blast- 

 ing can be done in safety. Considerable space is 

 devoted to safety-lamps, and it is pointed out how 

 great an influence the velocity of the air-currents 

 in the air-passages of a mine has on the safety of 

 a lamp. The electric lamp is perhaps the chief 

 hope of the miner, though it does not, like the 

 safety-lamp, indicate the presence of gas. The 

 commissioners arrived at the following conclu- 

 sions : "that it is most important that all mines 

 should be carefully examined by means of indi- 

 cators capable of detecting as small a proportion 

 as one per cent of gas ; such examination to be 

 made before the commencement of each day- 

 shift, and, in case of an interval, also before the 

 succeeding shift ; and that in all dry mines 

 where the air may be laden with coal-dust, and 

 where fire-damp is either known to be given off 

 from the strata, or may from experience be 

 reasonably suspected to exist, the secretary of 

 state may require safety-lamps to be used, unless 

 the owners and workmen of such mines prove 

 to the satisfaction of a court of arbitration, to be 

 appointed by the respective parties, that less 



liability to accident generally will be involved 

 by the working of the mine with open lights 

 than by use of safety-lamps. It should be a 

 special instruction to such court that the cir- 

 cumstances of each mine be taken into con- 

 sideration." 



The late Prof. John Morris, who died in Janu- 

 ary last, had been engaged for some time in 

 preparing a third edition of his invaluable 

 ' Catalogue of British fossils.' The first edition 

 was published in 1843, and the second in 1854. 

 From that date onwards, Professor Morris had 

 been collecting materials for a third edition, 

 which, unfortunately, he did not live to com- 

 plete. But his manuscripts have been placed in 

 the hands of a committee, which includes the 

 keeper of the geological department in the Nat- 

 ural history museum, the president of the Geo- 

 logical society, and other well-known geologists. 

 They have divided up the work among several 

 specialists, who have engaged to finish their re- 

 spective parts within six months ; and it is there- 

 fore hoped that this great work may be com- 

 pleted before very long. 



The publication of the Challenger volumes is 

 now proceeding rapidly. No less than fourteen 

 reports are at present passing through the press, 

 and it is expected that the entire series will be 

 completed by the end of next March. 



The Lumleian lectures, now in course of de- 

 livery before the College of physicians by Dr. W. 

 H. Stone, are attracting unusually large audiences. 

 Their subject is ' The electrical conditions of the 

 human body.' Dr. Stone was one of the first to 

 call attention to the importance of determining 

 accurately the physical constants of the agent 

 electricity when employed in physiological in- 

 vestigation. In these lectures he has shown that 

 most of the contradictory results obtained by the 

 earlier investigators are due to the neglect of 

 this precaution. The enormously high resistance 

 of the epidermis was demonstrated ; and, when 

 this was eliminated, the average resistance to a 

 continuous current from the ulna at the wrist 

 to the malleolus at the ankle, was shown to be 

 about 1,170 ohms, due allowance being made for 

 the errors caused by polarization, accordin- to 

 the ingenious method first devised by Sir Henry 

 Mance for the Persian Gulf cables. Some entirely 

 new experiments were detailed, and in part re- 

 peated before the audience, showing that the 

 human body could be charged and discharged 

 like a secondary battery. An electromotive force 

 of two volts was employed, and curves showing 

 the rate of discharge were exhibited. A dis- 

 charge current of sixty micro-amperes at first, 

 under an electromotive force of about one volt, 



