August 7, 1884] 



NA TURE 



355 



LETTERS TO THE EDITOR 

 [The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of, rejected manuscripts. 

 No notice is tahen of anonymous communications . 

 [The Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his space is so great 

 that it is impossible otherwise to insure the appearance even 

 of communications containing interesting and novel facts.] 

 " Gas-Burners, Old and New " 

 Permit me to point out a very obvious clerical error in the 

 notice, in last week's Nature (p. 270) of my little work having 

 the above title, and to make a few remarks concerning your 

 criticisms on the book. In the sentence, " ' Owen Merriman ' has 

 taken pains to insist on the two great desiderata of gas-burners — 

 high temperature and low temperature," the latter word is 

 doubtless intended for pressure : and the sentence should read 

 "high temperature and low pressure.'' It would have been 

 scarcely necessary to make this correction, but that the notice 

 may perhaps be read by many who are incapable of suggesting 

 the correct reading, and to whom therefore the sentence as it 

 \ ill be absolutely meaningless. 

 While fully appreciating the kindly nature and intent of your 

 criticisms, I cannot pass by, without a word of defence, your 

 statement that you think I have "gone too far in attempting to 

 give a popular theory of luminous combustion." I hope to be 

 able to show that the particular extracts from that portion of the 

 book to which exception is taken are practically correct, and, 

 so far as could be looked for in a work addressed to miscel- 

 laneous readers, sufficiently precise. To this end I will deal 

 with the various extracts seriatim. That "the various gases 

 which constitute ordinary coal-gas do not all burn together in 

 the flame " is a matter I had thought to be established beyond 

 reach of dispute. But if evidence is required of the truth of the 

 assertion, I need only point to a table prepared by Prof. 

 Landolt, showing the composition of gases in the different parts 

 of a gas flame, which is given by Prof. T. E. Thorpe, F. R. S. , 

 in a lecture on " Flame," forming one of the Manchestei 

 of Science Lectures (Manchester : John Heywood). By this 

 table it is clearly shown that in a gas flame, 3^ inches high, the 

 olefines, or heavy hydrocarbons, do not diminish in amount 

 until a height of 1 "58 inches is reached ; while the proportion of 

 .en i- considerably diminished at a height only of C39 

 inch. Although it may not be mathematically correct to say that 

 "the amount of light developed by any coal-gas flame is 

 ■■ rtional to the degree of intensity to which the tem- 

 perature of the carbon particles is raised," seeing that the light 

 emitted is not in exact proportion to the temperature of he 

 statement 'is sufficiently correct for a popular treatise. What 

 was chiefly intended to be enforced was that the amount of light 

 evolved from a gas flame increases with its temperature, and in 

 such a work a mathematical degree of exactitude is hardly 

 looked for. Now, with regard to the other matters which are 

 raised. To account for the destruction of luminosity which 

 occur, when air is introduced into a gas flame, two theorii 

 been put forward. According to the first, the heavy hydrocar- 

 bons at once meet with sufficient oxygen and are immediately 

 consumed, without their carbon being first raised to a white-hot 

 state ; but this theory alone will scarcely explain the phenomenon, 

 seeing that the effect of pure oxygen is to increase the lumin- 

 osity of aflame. The other and more rational theory — and die 

 one which is more generally accepted — supposes that the inert 

 nitrogen which is thereby introduced reduces the heat-intensity 

 of the flame "below the temperature required to decompose the 

 hydrocarbons." It may be that to some extent both causes are 

 at work. Lastly, as to the relative temperatures of a luminous 

 and a non-luminous flame. Although the average temper- 

 ature of the latter is higher than the former — as indeed it 

 must be, seeing that the same quantity of heat is contained in a 

 less -pace, the non-luminous flame nowhere develops so high a 

 temperature as is found at certain of the hottest portions of the 

 luminous flame. Mr. R. H. Patterson, in an article on the 

 action of the blowpipe considered with reference to the prin- 

 ciples of gas illumination (Journal of Gas :c. vol. 

 xxxv. p. 831), states that in the luminous region of an ordinary 

 gas flame he has succeeded in melting a platinum wire : a result 

 which he could never attain with a non-luminous flame." 

 July 21 .,- Merriman " 

 [We thank our correspondent for pointing o u the clerical 



error "low temper; '-'low pressure" in > 



We consider that the sentence, " The various simple ga 

 constitute ordinary coal do not all burn together in the flame ; 

 the temperature required to effect their ignition being lower for 

 some of them than for ol fhe 



■ild understan I in that the o 1 



having the lowest ignition point catches fire and burns away 

 first, and then the constituent of next lowest igniti 



■ and burns away, and so on ; wher ! 



show that the combustions are not distinct, but that 

 the rate of combustion of the hydrogen is grea 

 of combustion of the oth 



tiol think it " sufficiently correct " to say tl 



ere of the 

 coal-gas flame : perhaps it would be nearer the mark : 

 the intensity of the light varies as the fifth pow 



within certain limits. The admission of air into the 

 Bunsen flame destroys the luminosity more by dil 

 oxidation tl ration. — Ed.] 



The "Cotton-Spinner" 



1 1 n this British Holothurian (published in 



I on [une 12, ]>. 146), I drew a distinction between the 



kind of observations that were possible to a student in a museum 



and to one who was working at a laboratory specially adapted 



for biological investigation and situated on the sea-shore. 



The experiences of the last few da} s have shown me only too 

 well that this distinction was not overdrawn or too refined. By 

 the kindness of Mr. John Snell of Truro, I have been favoured 

 with two consignments of the "Cotton-Spinner;" three speci- 

 mens which reached me on Monday by parcels post gave 

 sufficient evidence of having died some hours before. This 

 hap induced me to propose to Mr. Snell that he should sen 

 specimens by express, and entrust them to the charge of the 

 guard of the train ; for this suggestion I am indebted to Dr. 

 Gunther. Mr. Snell not only did this to-day, but he was good 

 enough also to warn me by telegram that the specimens would 

 reach Paddington at 8 p.m. this evening. I was at the station 

 to meet them, and I have no doubt that the comparatively fresh 

 condition of the sea water was due to the attention of the gu rd 

 of the train. Notwithstanding all this care and trouble, the 

 three "Cotton-Spinners" were dead. 



I have given this detailed, and, I fear, tedious expositi 

 the whole case, because it seems to me to clench the argument 

 that the problems of the physiology of marine forms, and 

 daily of those less-known creatures which live at a depth 

 like the "Cotton-Spinner" — ten to twenty fathoms, arc not 

 soluble at some distance from the coast, however great be the 

 trouble or the care that is taken in forwarding them. We must 

 have a laboratory on the sea-shore. 



The only fact that I have been able to observe is that the 

 threads of the "Cotton-Spinner" do undoubtedly attach them- 

 selves to objects in their vicinity : one of the specimens obi 

 this evening was attached to sea-weed ; from the cloacal orifice 

 a connected strand of threads, about one-fifth of an inch in width 

 and an inch in length, spread out at its free end into a number of 

 more free threads which had attached themselves to the sea- 

 weed which had been placed in the water ; they extend 

 about two inches in breadth. From what I have learnt of the 

 extensile and swelling power of these threads, I should t 

 that about as much had been expelled as would occupy the 

 greater part of the cloacal cavity. A woodcut illustratii 

 cloacal cavity so filled by tubes, and drawn from a spirit 

 men preserved in the British Museum, wdll be given in my 

 paper on this animal, which will be published in the next 

 (October) part of the P. . he Zoological S< 



August 1 F. Jefferv 



Krakatoa 



I MOST respectfully beg to point out to you a fev. 1 

 in the English version of my ''Short Report on 

 Eruption," published in Nature, M 



It says on p. 15 : — " In this eruption very ci 

 were ejected, i.e. very smooth, round balls, resembling 11 

 to the size of ij to 6 centimetres in diameter. 

 of acids : they contain 55 per cent, carbonate of lim< . 



The words italicised are wrong, i 



. .it. which means " hey strongly , 



