2S4 



NA TURE 



[July 19, 1894 



The extinctive proportions <■■ u.c i;.i^ for the flames of various 

 Rises burnt from a jet, on the other hand, showed wide dif- 

 ferences. The minimum percentages of carbon dioxide gas in 

 air required for the extinction of the various flames of gases 

 were as follows : for hydrogen, 5S ; for carbon monoxide, 

 24 ; methane, 10 ; ethylene, 26 ; and for coal-gas, 33. These 

 numbers show no relation, as they might have been expected 

 to do, to the %'olume of oxygen necessary for the combustion of 

 th- different gases. 



A second series of experiments was then undertaken to ascer- 

 tain the minimum proportion of nitrogen which must be added 

 to the air in order to render it extinctive of the various flames 

 already specified. It was found necessary in every case to add 

 nitrogen in larger proportion than carbon dioxide to the air, in 

 order to secure the extinction of a flame. The superior ex- 

 tinctive power of carbon dioxide over that of nitrogen is 

 probably connected with its higher specific heat, and with its 

 greater density. 



Characteristic differences were noticed between the behaviour 

 of wick-fed flames and flames supplied with gas from a jet, 

 during the process of their extinction. The wick-fed flame 

 gradually dimiuisheJ in size until it ultimately dwindled away. 

 The gas-fed flame, on the other hand, rapidly iiiirtaseJ in 

 dimensions, at the same time becoming more and more pale ; 

 and it became so pale at last as to be often visible with diffi- 

 culty, so that it was not easy to mark the moment of its 

 extinction. Probably the extinction of both classes of flames 

 was primarily due to the lowering of their temperatures. In 

 the case of (he wick-fed flames, however, the reduction of their 

 temperature led to the diminution of the supply of gaseous and 

 vapourous fuel to the flame, and the flame ultimalely died 

 because it was starved. In the case of gas fed flame the supply 

 of fuel, being independent of the flame, was maintained, and 

 ihe flame perished from lowering of temperature only ; in ils 

 eflTort to obtain an adequate supply of oxygen in the diluted 

 air, however, it expanded its surface, and it thus undoubtedly 

 hastened the reduction of temperature which led to its 

 extinction. 



The very high proportion of carbon dioxide in air which is 

 necessary for ifie extinction of the hydrogen flame has received 

 an important and interesting application. One of the most 

 serious troubles to which the miner is exposed when using his 

 safety-lamp, is the exrinction of its flame by air containing 

 carbon dioxide. In most mines the lamp cannot be relighted 

 with safety, since a naked flame would cause danger in the 

 possible presence of inflammable gas. The loss of the flame 

 therefore implies the necessity of the miner moving in darkness 

 often through a considerable distance to a place where the wick 

 may be relighted without risk. The safety-lamp for delicate 

 and accurate gas-testiog, which has been already described by 

 the author 'AVj'. Soc. /-roc. vol. Hi. p. 486), provides the means 

 of avoiding this inconvenience and possible danger. Wilhout 

 opening this lamp it can be made to burn either an oidinary oil- 

 flame alone, or a hydrogen flame alone, or both these flames 

 maybe made to barn side by side. If the miner is approach- 

 ing a part of the mine in which the proportion of carbon dioxide 

 may be extinctive of his oil-flame, he would turn on ihe hydrogen- 

 flame as an auxiliary. If the oil-flame becomes extinguished, he 

 has proof that he has entered air containing at least fifteen per 

 cent, of carbon dioxide; but he can withdraw from it with his 

 hydrogen-flame still burning, and in purer air the hydrogen- 

 flame will at once rekindle ihe wick and give him his illumina- 

 ting flame once more. Under certain circumsiancts he might 

 even with safety pass though the loul air, and in a similar way 

 regain his oil flame. Ii is even possible to arrange the 

 hydrogen-jet so close lo the wick, that the oil-flime is more or 

 less perfectly maintained by the hydrogen-flame even in the 

 presence of much carbon dioxide. 



The question h.ns Keen raised whether it is safe to enter air 

 which contains sulncicnt carbon dioxide to extinguish a candle- 

 flame. This question is usually answered in the negative. Hut 

 recent experiments made by J. R. Wilson {Anier. Journ. Pharm. 

 50, No. 12), seem to prove that rabbits can breathe fur an hour 

 with entire immunity Irom harm or even discomfort air containing 

 25 per cent, of admixed carbon dioxide, and that when the air 

 contains 50 per cent, of the gas it is by nomcans immediately fatal 

 to a rabbit which is immersed in it. Now air containing 15 i>cr 

 cent, of carbon dioxide at once extinguishes an ordinary c.imllc- 

 flame or oil-flame. Ilcnce it appears that nir may contain a 

 considerably larger proportion of carbon dioxide than thai which 



NO. 1290, VOL. 50] 



is necessary to extinguish the flame of a lamp or candle, and 

 yet be competent to maintain life when it is breathed. This 

 statement is fully supported by experiments made by Dr. Angus 

 Smith, as well as by the experience of miners and others. 



The following conclusions may be drawn from the experiments 

 referred to above : — 



(1) That the extinction of a flame depends not only upon the 

 iiuattlily but also upon the quality of the extinctive gas present 

 in the air; carbon dioxide uniformly exerting a more powerfully 

 extinctive effect than nitrogen. 



(2) That wick-fed fl.imes burning different combustibles show 

 a remarkable uniformity in the minimum proportion of an ex- 

 tinctive gas in air necessary for their extinction. 



(3) That this uniformity is not shown by flames fed by a gas 

 burning from a jet ; and no simple relation is .apparent in the 

 case of the gas-fed flames between the proportion of oxygen 

 present in the diluted air and the proportion of oxygen re- 

 quisite for the complete combustion ol the gas. 



(4) That the hydrogen flame requires for its extinction the 

 presence in air of a very high proportion of extinctive gas ; it 

 may therefore be advantageously used as an auxiliary flame 

 for maintaining an oil- flame in the foul air of a mine or 

 other locality. 



(5) Since an ordinary candle-flame or oil-flame is extin- 

 guished by the presence of about 15 per cent, of carbon dioxide 

 in air, and air containing over 25 per cent, of carbon dioxide has 

 been breathed with perfect safety for more than an hour, the 

 extinction of an ordinary oil- or candle-flame in any particular 

 atmosphere must not be taken as proof that that atmosphere 

 contains so much carbon dioxide as to be dangerous lo life when 

 it is breathed. 



(6) \ moie satisfactory indication of the presence of a 

 dangerous proportion of carbon dioxide is furnished by the 

 change of colour of the hydrogen flame from reddish to blue- 

 grey. This change begins when 2 per cent, of carbon dioxide 

 is present in the air ; it becomes very pronounced as the pro- 

 portion of the gas present increases. When 30 per cent, or 

 upwards is present the flame is of a pronounced blue colour and 

 also increases in height with the increased proportion of the gas, 

 to an extent which is easily measured on a scale. 



May 31. — " Note on the Possibility of obtaining a Unidirec- 

 tional Current to Earth from the Mains of an Alternating 

 Current System." By Major P. Cardew. 



June 21. — "Degenerations consequent on Experimental 

 Lesions of the Cerebellum." By Dr. J. S. Risien Russell. 



The paths which degenerate after aLilation of one lateral lobe 

 of the cerebellum, and .ifter extirpation of its middle lobe, 

 are discussed in this paper. 



Degenerated fibres are found in all the peduncles on the same 

 side after Ihe former operation, and in the superior peduncle of 

 the opposite side. The position occupied by these degenerated 

 fibres, in this peduncle, is that of fibres which degenerate in both 

 superior jieduncles alter the cerebellum has been divided into 

 two lateral halves by a mesial incision. The degenerated fibres 

 in the superior peduncle of the side of the lesion decussate in 

 the posterior quadrigeminal region, and p.assto the opposite red 

 nucleus and optic thalamus. Tho^e fibres which degenerate in 

 Ihe middle peduncle pass chiefly to the grey matter of Ihe 

 opposite side of the pons. Of the fibres which degenerate in 

 the inferior peduncle, the ni.ajority occujiy the lateral region of 

 the medulla, becoming more and more scattered as they pas< 

 down. These can no longer be said lo form a tract below thr 

 level of Ihe superior pyramidal decussation ; but a few scat- 

 tered fibres occupy the anlero-laleral region of the cervical 

 cord, beyond which none can be traced. Degenerated filires 

 pass to both inferior olives from this peduncle ; but no well- 

 marked tract to the opposite inferior olive was found. 



After extirpation of the nii(Ulle lobe of Ihe cerebellum, 

 degenerated fibres were found in all ihe peduncles. Those in 

 the superior peduncle decussaie in the region of the posterior 

 corpora quadrigcmini, and terminate in the opposite red nucleus. 

 The degenerated fibres in the middle peduncle behave much as 

 ill) those which result from ablation of one lateral lobe of Ihc 

 cerebellum ; and the same may he said with regard to Ihe 

 degenerated fibres in the inferior peduncle. 



No degeneration was found in the fillet, posterior longiunlinal 

 bundles, pyramids, ascending tool ol the filth nerve, the root 

 of ihe cranial and spinal nerves, and in ihc spinal cord, forming 

 an anlero-laleral Iracl throughout ils whole length. 



