UNDULATORY FORCES. LIGHT. 



[(JA8 FKOM OILS. 



per-centage of the amount of condensation by the time 

 required to burn a cubic foot ; and in this way he obtains 

 a remit that may be said to represent the true value of 

 the gaa. Suppose that one gas, which he takes as a 

 stamlard, has a condensation of 4 -33, and a durability 

 of 50-5 minute* these multiplied together make 2187, 

 which may be called the value of the gaa. Another gas has 

 a condensation of 7 -55, and a durability of 57 minutes ; 

 these multiplied together give a value of 430'3. Now if 

 we call the standard number of the former 1, that of the 

 second will be 1 -95 ; and thus we obtain their relative 

 valuta. The following table is constructed on this 

 principle : 



Go from Condensation 



by chlorine. 



4-33 . 



Durability of a 

 cubic foot. 



60" SO- 

 SO' 40" 

 62' 30" 

 67' 0" 

 62* 

 CO' 



Rrlatlre 

 value. 



1-00 



1-50 

 1-85 

 1-93 

 3-40 

 3-66 

 6-07 

 5-46 

 6-69 

 776 

 8-32 



English caking coal 1 



(Newcastle) . . J 

 Peareth and Pel ton . . 6-50 

 Yorkshire Parrot . . 7 '66 

 English cannel (Wigan) 7 '55 

 Ramsay Parrot . . . 12-00 . 62" 0" 

 Mid-lothian . ... 13-00 . 60' 0" 



Lesmahago IT'10 . 65' 0" 



Scottish Parrot . . . 15-00 . 80" 0" 



Wemyss 19-50 . 75' 0" 



Kirkness 2070 . 80" 0" 



Boghead 22'40 . 81' 3" 



It will be noticed, that when the value of a gas is tested 

 in this manner, it indicates a higher quality than we can 

 obtain by means of the photometer ; but this Dr. Fyfe 

 regards not as an error in his process, but rather as an 

 evidence that we do not take the best means to burn the 

 gas to the best advantage ; and consequently that the 

 illuminating power is, in the case of the richer cannels, a 

 little below its true value. 



As a corollary to the preceding, we append a table, 

 which shows the quantity of gas furnished by different 

 varieties of coal, together with the specific gravity of the 

 gas, its illuminating power in sperm candles of 120 grains 

 each, its per-centage of condensation by bromine, and its 

 actual value in sperm caudles. This table has been com- 

 piled from the results obtained by Mr. Evans, Mr. 

 Thompson, Dr. Letheby, and others. 



Oil Oat. Originally tliis was the gas most generally 

 in use for illuminating purposes; but the cost of its 

 manufacture was found to be too great for its continued 

 employment. 



As far back as the year 1805, Dr. Henry published an 

 account of some experiments which he made on a gas ob- 

 tained from sperm oil, and he showed that in illumi- 

 nating power it was the only one which could compete 

 with olefiant gas. Soon after that, Messrs. J. and P. 

 Taylor contrived an apparatus for procuring it on a 

 Urge scale. Their apparatus consisted of a furnace in 

 which was placed a twisted iron tube, containing frag- 

 ments of coka The object of this arrangement was to 



! increase, as much as possible, the extent of the heating 

 and decomposing surface. When the tube was red-hot, 

 oil was suffered to run into it in a small but continuous 

 stream. In this way the oil was decomposed and re- 

 solved into inflammable vapour, winch escaped, and a 

 fine spongy charcoal, which remained behind. The gases 

 evolved were merely washed with water, and then collected 

 in a gasometer. By this process it was found, that a 

 gallon of whale-oil yielded about ninety cubic feet of 

 gas, which liad a specific gravity of 900, and was about 

 twice as rich in illuminating principles as the best de- 

 scription of coal gas. Other patentees, as Mr. English, 

 Mr. Booth, and others, followed in the same course, and 

 endeavoured to perfect the process so as to work it on an 

 economical scale ; but notwithstanding that every moans 

 were token to accomplish this, and that the commonest 

 oils were used for the production of the gas, it was 

 found that it could not compete with the cheaper gas 

 obtained from coal: and therefore the process was 

 abandoned. 



An attempt was made to revive it by a company 

 wliich adopted the name of the Vegetable Gas Company 

 but the attempt has not been successful. Nevertheless, 

 it may be said, that where coal gas is very dear, or not to 

 be obtained at all, or where, for sanitary or other pur- 

 poses, an unusually pure gas is required, then the 

 process of making oil-gas may be practised with ad- 

 vantage. To meet such 'cases, a small apparatus lias 

 been contrived by Mr. Skelton ; and a somewhat similar 

 one is sold by Messrs. Burgess and Key, of Little 

 Britain. The latter consists of a small cylinder B 

 125), fitted into Fig. 129. 



a furnace C, so 

 that it may be 

 made red-hot. 

 A reservoir I, 

 containing oil, 

 or refuse fat, is 

 suspended near 

 the chimney of 

 the furnace G, 

 and when the 

 fat is perfectly 

 liquid it is al- 

 lowed to drip 

 from a small 

 tap into a syphon pipe'E, whence it runs into the red- 

 hot cylinder, and is decomposed. The evolved gases 

 escape by the tube F, and are conveyed by J into a 

 purifier D, which contains water; the delivery tube M 

 dips an inch or so under water, in order that the gas 

 may be washed and cooled. The tube K L transmits 

 the gas from the purifier into the gasometer A. The 

 gas which is produced in this manner is of high illumi- 

 nating power ; and it appears, from the statements made 

 by the venders of the apparatus, that a pound of kitclicii- 

 stuff yields from ten to eleven cubic feet of gas. Now a 

 pound of this material weighs 7,000 grains ; and as the 

 gas produced weighs only about 5,000 grains, there is 

 manifestly a loss of nearly one-third. This occurs in the 

 form of charcoal, wliich remains in the retort; and 

 hence the necessity for a frequent cleaning out of this 

 part of the apparatus. Dr. Fyfe states that the loss in 

 his experiments was much greater that it amounted to 

 nearly one-half of the fat used ; and the same remark is 

 also made by Mr. Wright, who has reported upon the 

 comparative economy of the vegetable-gas scheme. The 

 latter gentleman states, that for a gallon of 91bs., the 

 waste amounts to 2 II PS. 10 oz. 



The gas which is produced from oil is of high specific 

 gravity, and ranges between 700 and 900. It contains 

 from 30 to 40 per cent, of rich hydro-carbons, which may 

 be condensed by chlorine and bromine : of these about 

 20 per cent, are absorbed by anhydrous sulphuric 

 acid : 100 volumes of the gas require about 260 volumes 

 of oxygen for their consumption, and they yield 158 

 volumes of carbonic acid. The durability of the gas, 

 with Dr. Fyfe's four-inch flame from a jet the -jiyrd of 

 an inch in diameter, is 68' 20" ; consequently, its value is 



