366 



NAT^URE 



\J\Iar. 7,187: 



" The body of the respirator is about 4in. or 5 in. lon<j, 

 and contains at the top a layer of cotton wool, moistened 

 with glycerine to prevent any solid particles escaping into 

 the mouth from lower layers, and also to stop those very 

 minute particles of the smoke that may not have been 

 arrested below. Next comes a layer of dry cotton wool, 

 then a layer of charcoal fragments, another layer of dry 

 cotton wool, and then some fragments of slaked lime. 

 Below this comes some more cotton wool, and then the 

 wire-gauze cover or cap at the bottom.* 



" For smoke the layer of linte is not necessary, but in 

 the mines it would be of the greatest use, because it has 

 a great attraction for COo. The layer of charcoal would 

 absorb the CO and the HS in the air, and the mixture in- 

 haled would be perfectly innocuous. The disadvantages 

 of this respirator in its present form for mining purposes 

 are — that it is too long, and an effort is required in breath- 

 ing through the small valves.t Mr. Ladd, of Beak Street, 

 Regent Street, the maker of these respirators, has made 

 some improvements in the mouth-piece, which may over- 

 come some of the inconveniences of the old pattern. 



" I received permission to use the R.E. workshops for 

 experimenting on the shape best suited for use in the 

 mines. Tyndall's respirator has been severely tested in 

 dense and pungent smoke from pinewood, and it succeeded 

 to the perfect satisfaction of Captain Shaw, Chief Officer 

 of the London Fire Brigade. Firemen are to wear it 

 attached to hide helmets, but for the mines any arrange- 

 ment which will support the respirator and keep it close 

 to the mouth during work, without being hot or uncom- 

 fortable, will suffice. 



" Experiments made ivitJi the Respirator. — On Satur- 

 day, August 19, 1 87 1, a trial of the respirator was made 

 in the Chemical Laboratory, S.M.E,, in the presence of 

 Colonel Lennox, Dr. Fox, and others. I was shut up in 

 an air-tight cupboard, with the respirator on. By my 

 side were jars containing CO and CO^ in a proportion of 

 j^ each of the cubic content of the cupboard (i4i,598'4 

 cubic in.), not allowing for the space occupied by my 

 own body and the stool on which I sat. The respirator 

 contained animal charcoal and lumps of slaked lime 

 mixed together, thus dispensing with one layer of cotton 

 wool. After emptying all the jars, 1 remained for ten 

 minutes in the full mixture (fifteen minutes in all) without 

 the slightest discomfort except from the awkward shape 

 of the respirator. I was then called out. 



"On Monday, the 21st, another trial was made in the 

 presence of Dr. Fox and Lieuts. Abney and Galwey. 

 This time a rabbit and three birds were placed in the cup- 

 board with me. The respirator contained, in addition to 

 the charcoal and slaked lime, a small quantity of sul- 

 phate of soda. The only cotton wool used was a small 

 layer soaked J in glycerine at the top, and a thin layer of 

 dry wool at the bottom. The sulphate of soda was intro- 

 duced according to Prof Graham's advice, in order to 

 give an atom of O to the CO to form CO,, becoming itself 

 sulphite of soda. The content of the cupboard is 

 I4I,69S'4 cubic in. : from this would have to be deducted 

 the space taken up by my body, say 3,} cubic ft. (Dr. 

 Parke's Hygiene), or, roughly, 6,000 cubic in., leaving 

 •35,698 cubic in. 1,890 cubic in. of CO, in jars were 

 introduced from a pressure bag, making altogether : — 



1,890 cubic in. of COo 

 1,921 cubic ill. of CO, 



or 3,811 cubic in. of poisonous gases in addition to my 

 exhaled breath, or about 3 per cent, of the capacity of the 

 cupboard. In order to perfect the mixture of the gases, 

 I waved a towel about constantly, and after the end of 



* This order may be varied in difterent ways witliout prejudice to tlie 

 respirator. 



t These objections have been In great part met by the recent forms of 

 the respirator. 



J See remark in the introduction above. 



the trial, a taper being extinguished at the top of the 

 cupboard showed that the CO, had been stirred up to 

 the top. The rabbit and two birds died at the same time, 

 about twenty-three minutes after the cupb lard was closed, 

 while the CO from the pressure bag was being introduced. 

 I stayed in the cupboard thirty minutes (five minutes after 

 the mixture was completed and seven minutes after the 

 death of the animals). When I came out I felt a pressure 

 on my ears, as when descending too rapidly ni diving. 

 Dr. Fox said that this was produced by my blood, my 

 heart then beating at a high rate. 



" This is satisfactory, as showing that the gases had not 

 affected me, but only the exertion of breathing through 

 the respirator, for thirty minutes, combined with the heat 

 of the close atmosphere in wliich I was. 



" To prove that the gases did not affect me, I quote some 

 extracts from Dr. Park's ' Hygiene ' : — ' Dr. Angus Smith 

 says the breathing of CO, to the extent of i'5 to 2 per cent, 

 produces slowness of heart action, while the respirations 

 become quickened if not gasping ; this is perceptible with 

 as little as 'i per cent. Less than \ per cent, of CO has 

 produced poisonous symptoms, and more than i per cent, 

 is rapidly fatal to animals. CO in excess produces loss 

 of consciousness, slowness of heart action, and finally 

 paralysis of the heart. 



" The slowness of diffusion of the two gases was 

 remarkably shown by the effect on the third bird. 

 The cage which held it was suspended at the top of 

 the cupboard. The bottom, back, and top were of 

 wood, the other sides were of wood for about \\ in. 

 and then of wire. The bird, which was at first on a 

 perch, was very seon affected by the impure air, and fell 

 to the bottom of the cage. Here the wooden bottom and 

 sides evidently supported a layer of pure air, for although 

 the bird had lost consciousness, and indeed was con- 

 sidered to be dead, yet after being brought out into fresh 

 air, it was revived by ammonia, and after an hour or so 

 fluttered away. The other animals, that were not so pro- 

 tected, died before all the gases had been introduced. 



"On examining the sulphate of soda, very little was found 

 to have been changed into the sulphite ; it would, there- 

 fore, seem that a constant change occurred, the sulphate 

 giving up oxygen to the CO, becoming sulphite, and then 

 the sulphite taking oxygen from the air to form the 

 sulphate. Whether the good effect of the first change 

 compensates for the loss of free oxygen in the second 

 change is a question for the opinion of a chemist ; how- 

 ever. Prof. Graham's recommendation is of great weight. 



" All that were present agreed that the trial was per- 

 fectly satisfactory, and I think this is a fair conclusion. 

 For the object in view throughout has been to devise 

 some plan by which a man may work for some time in a 

 foul mine, and may be secure from the effects of a rush 

 of foul gas caused in untamping, &c. 



" Defensive mines, though small, poison the ground 

 more effectively than overcharged mines, which allow 

 most of the gas to escape. 1 have before snown the tot.al 

 amount of CO and CO^ evolved by the explosion of 100 lbs. 

 of powder, which, according to our late operations, seems 

 to be an average charge. It is probable that a large pro- 

 portion of these gases would escape into the air, and that 

 the rest would be diffused equally all round the charge. 

 Therefore only a small amount is likely to be encountered 

 at any one point. Hence it would seem that the respirator, 

 which has succeeded with very powerful mixtures of 

 poisoned air, would be quite enough to guard the miners 

 from any of the gases from explosions. 



" It only remains now to hit upon a convenient shape 

 which will not render the breathing laborious. If we suc- 

 ceed in this, it is likely that the respirator would be of use 

 also in civil work, such as exploring mines in search of 

 bodies after a colliery accident."* 



J. E. G. 



* This is one of the purposes contemplated by myself, but the suggestion 

 of Mr. Gibbs is independent and origiual.— J. T. 



