Mar. 7, 1872] 



NATURE 



565 



nearly the temperature of the outer glass in which the blackened 

 thermometer is enclosed), we have not indeed an absolute mea- 

 sure of solar intensity ; for all measures of that must, it would 

 seem, depend on the substance exposed and the conditions as to 

 cooling, (ic, under which the exposure takes place, but a sensi- 

 tive test by which slight variations in its amount can be deter- 

 mined, and the amount at different places and different times 

 compared. F. W. Stow 



The Aurora of February 4 



The following is an account of the aurora of February 4 as 

 seen by a gentleman living in Russia, at Anspatti, in the province 

 of Vitebsk. After stating that the barometer had risen very 

 high (30'2), he says: — "To-night, as I drove home from 

 Reugarten, there was the most beautiful aurora borealis I ever 

 saw. It began in the north-west, and gradually rose higher and 

 higher, till at last it reached the horizon a little north of east, 

 and such a broad band, or rather succession of bands, that it 

 covered half the heavens. It was a bright rose colour, and its 

 light and colour were reflected by the snow, so that the whole 

 earth was rosy ; though it was between nine and ten o'clock, and 

 there was no moon, it was nearly as light at day. It is still in 

 full force as I am writing, and I can see it from my window, but 

 it constantly changes its ibrm and colour." I think the latitude 

 of the place is 56 or 57. J. M. li. 



Aurora Island 



Nature for May 25 (which has only just reached this part of 

 the world) contains a note respecting the reported disappearance 

 of Aurora Island in the New Hebrides. In that note the small 

 upraised coral island of that name north-east of Tahiti is con- 

 founded with Aurora — a high volcanic island — more than 40 '^ to 

 the west of the former. It is scarcely to be wondered at that 

 the mistake should be made when the name of the island 

 is alone given; but when "Aurora Island, one of the New 

 Hebrides group," is spoken of as being to the " north-eastward" 

 of the well-known island of Tahiti one feels surprised at the mis- 

 conception. 



Has it yet been clearly defined to which Aurora the report 

 refers, and is it not more probable that the captain's chronometer 

 was out, or that his reckoning was incorrect, than that either 

 island has really been submerged ? A few months .ago Dr. 

 George Bennett, F. L.S., of Sydney, New South Wales, showed 

 me a sketch which he made of Aurora in the New Hebrides some 

 years ago. From that the island appears very mountainous, and 

 the map' of Melanesia, in Petermann's Geographische Mittheil- 

 ungen (1870), makes it about twenty miles long and 2,cx30ft. high. 



S. J. Whit.mee 



Samoa, South Pacific, Nov. 4, 1871 



P.S. — The followmg notes of earthquakes in the Samoa group 



may be of interest to some of your readers : — 



May 14, 1871. — 2.5 r.M. First a vertical, followed by a hori- 

 zontal, shock. 



July I, ,, — 9. 30 A.M. Slight horizontal shock. 

 ,, 16, ,, — 12. 10 P.M. Vertical shock. 



Aug. 3, ,, — 12.15 P'"' Slight horizontal shock, accom- 

 panied by a loud rumbling noise. 



Sept. 23, ,, — 6.45 A.M. A slight horizontal shock. 



I was absent from Samoa from September 1S70 to April 1S71. 



During that time there were eight shocks of earthquake in the 



group ; but the dates and other particulars were not noted. One 



is reported as having been the most severe shock known here. 



Earthquakes have been more frequent in Samoa for the past year 



or two than formerly. 



FOUL AIR IN MINES AND HOW TO LIVE 



IN IT 



I. 



I BEG to forward you for publication in NATURE 

 an account of some very interesting experiments 

 recently made at Chatham, on the employment of a res- 

 pirator in military mining. They were conducted in a 



thoroughly practical manner by Mr. J. Edward Gibbs, a 

 highly intelligent young officer of Engineers, who, I may 

 add, has given the respirator a very convenient form, and, 

 I trust, will continue the work he has so well begun. 



It is to be borne in mind that the cotton wool employed 

 in the respirator is not to be stt'cpcd in glycerine, but 

 moistened with this substance ; the wool ought to be well 

 teased until all its fibres are wettedb, ut they must not form 

 a clot. John Tyndall 



" When on duty at the Defensive Mines one day 

 during the mining operations of July and August 1871, 

 three men were brought out in a fainting state, caused by 

 a rush of foul air in untamping. Thinking some means 

 might be devised for preventing such accidents, and the 

 consequent loss of time and panic, I consulted with 

 Captain Malcolm, R.E., who proposed Prof. Tyndall's 

 firemen's respirator for consideration. Colonel Lennox 

 sent me to the maker to inquire, and I returned with one. 



"With the assistance of Quartermaster-Sergeant In- 

 gram of the Chemical Laboratory, and several books of 

 reference, I have collected the following notes : — 



" After exploding a charge of gunpowder at a gallery- 

 head, it becomes dangerous to untamp, because of the 

 poisonous gases produced by the combustion of the 

 powder. These gases are CO,, N, CO, HS, C.H^, and II. 

 The only gases that are present in sufficient quantities to 

 harm are C0„ and CO. CO, to the amount of Tr^m ('005) 

 of the bulk of the air at the gallery-head would render it 

 unfit to sustain life. CO to the amount of ^Ja ('oi) would 

 do the same. 100 lbs. of powder evolve 225593S 

 cubic in. of gas at 60^ F. and 30" B., of which 94297896 

 are CO,, and 2249"848 are CO. 



" Miners working in the presence of the foul air from 

 the explosion suffer in two ways. If affected sud- 

 denly, they feel a burning at the nape of the neck, and 

 their limbs tremble, they turn giddy and faint. This 

 is to be attributed chiefly to the CO. The miners are 

 also affected in a slower manner by the CO.j. They feel 

 their breathing becoming difficult, as if there were a 

 weight on their chest, with a tight feeling in the head ; if 

 not brought into the fresh air they are in time overcome 

 and faint. This also brings on headache, on coming into 

 fresh air. 



" Any method of getting rid of the foul gases by che- 

 mical means must interfere greatly with the progress of 

 the work. In any case there would be considerable diffi- 

 culty in destroying the CO, as it has neither acid nor 

 basic properties. A good system of ventilation through 

 hose would clear the galleries of the foul air, but would 

 not overcome the difficulty of untamping, because at any 

 moment of the process there may be a rush of foul gas, 

 which would take effect on the men at work, before the 

 ventilation could carry it away. 



" A good respirator worn by each of the men employed 

 at untamping might overcome this difficulty. Prof. 

 Tyndall's respirator for firemen is constructed with a view 

 to enable the men to inhale pure air when at work in a 

 burning house, by separating the smoke and noxious 

 vapours. It consists of two parts; (i) the mouth-piece ; 

 (2) the body of the respirator. 



" The mouth-piece is an invention of a Mr. Carrick, 

 hotel-keeper at Glasgow, who had patented it.* It has 

 two valves, /and e. (See Nature, June 15, 1S71.) The 

 air inhaled comes from below, up through the body of the 

 respirator and through /. The exhaled breath closes /, 

 and escapes through e, thus keeping the contents of the 

 body of the respirator cool. There is an aperture o, which 

 fits closely round the lips, and to prevent respiration 

 through the nose, there is a nose-pad fixed on top of the 

 mouth-piece. A wire-gauze partition separates the mouth- 

 piece from the contents of the body of the respirator. 



* This is not the mouth-piece now adopteJ.— J.T. 



