FOSSIL HYDRO-CARBONS, THE SOURCE OF LIGHT, HEAT, COLOUR, ETC. 215 



from it. It is used in paper-making, like rosin, but is chiefly employed by 

 chemists for plaisters, and also for incense. 



Rosin-oil used to be imported from America, the common dark fetching 

 6s. to 7s. per cwt., and the fine pale 12s. to 14s. It is used for burning, 

 lubricating machinery, &c, but the new American earth-oils have materi- 

 ally interfered with its sale. * 



FOSSIL HYDRO-CARBONS — THE SOURCE OF LIGHT, HEAT, 



COLOUR, ETC. 



BY THOMAS D. ROCK. 



Part III. 

 Having already given, to readers of the Technologist, an outline 

 description of those industries connected with the subject before us, as well 

 as a brief account of the raw material in its distinctive varieties, I propose 

 in this third, and concluding paper, to consider the hydro-carbons collec- 

 tively in respect of their practical utility to man ; and in enumerating 

 some of the various applications of these interesting substances, I shall 

 preserve the order above mentioned, and notice their value consecutively 

 aa sources of Light, Heat, Colour, &c. 



Light. 

 Artificial light is an important element of comfort in modern civili- 

 zation, and the nearer it approaches in brilliancy and effect to the genuine 

 light of day, the greater its value and efficacy. Our ancestors, as well as 

 the forefathers of all the present European nations, contented themselves 

 with very dim substitutes for the glorious orb. Lamps for burning limpid 

 oil, and those not constructed upon Moderator principles, furnished the 

 chief supply of artificial light ; or solid fats and waxes were formed into 

 candles, with wicks that would be reckoned abominable in these days of 

 useful progress. But now all is changed ; and without, in any measure, 

 commending the altered and nocturnal habits of the people, induced, or 

 encouraged, it may be, by the increased brilliancy and superior character of 

 our illuminating agents, it is, nevertheless, impossible to deny, that, so far 

 as the light itself is concerned, the improvement contributes much to our 

 physical, as well as mental, enjoyment. Contrast the dingy and melancholy 

 aspect of the thoroughfares as they appeared in the early days of many 

 who will peruse these lines, with the cheerful gas-illumined street of 

 recent times ; or the sombre interior of our public institutions and churches 

 of the past with those of the present, as they appear radiate with brightness 

 streaming from innumerable jets of flame, as it were mysteriously inex- 

 haustible ; and the gain is obvious. The social and family hearths likewise 



