88 CONSTRUCTION OF RETORTS. 



At the end of fifteen months, or when a bench of ordinary retorts is worked 

 out, they may be replaced for 38 3s., as stated at page 70. And sup- 

 posing the wear and tear of the proposed retorts to be the same, at the end 

 of fifteen months they would require to be replaced also, which would be done 

 for about 43 18s. All the machinery, except the retorts and webs, will 

 last for years without any repair, except what may arise from contingencies, 

 to which all machinery is subject. 



The minor advantages attendant upon this form are, that it occupies less 

 space ; the stokers (so called at present) might be spared that name ; the 

 heat would not be felt more than in a boiler-house, and the retort-house might 

 be kept perfectly clean, wholesome, and free from suffocating vapour. 



The web may be repaired at any time, or even made in the first instance 

 by a labourer. After it has been at work some time, the plates of which it is 

 formed, by their contact with carbon at a red heat, become converted into 

 excellent steel, and might be sold for a sum at which a new web could be 

 constructed. 



If I were to become the lessee of any gas-works, I should undoubtedly use 

 this plan, being quite confident that the extra expense of their first erection 

 would be more than returned to me at the end of the first year. 



It is well known to every one connected with the manufacture of coal-gas 

 that a thin stratum is desirable. Chemistry will point out the various causes 

 and effects, and I have already shown that the quantity of tar and ammoniacal 

 liquor is much increased when the coal is acted upon slowly, as the centre por- 

 tion must be when decomposed in mass. By the means just described, the con- 

 version of the vapours and rich products of the coal is properly effected, and 

 no deposition of carbon takes place, as the gas passes away immediately on its 

 formation. These advantages, combined with the saving of tools and labour, 

 will fully justify my statement of the advantages attendant upon this form. 



EARTHEN RETORTS. 



IN speaking of clay or earthen retorts, it is necessary to limit my remarks 

 upon them to the results of practice ; for in many instances, owing to actions 

 not entirely and clearly accounted for, the results given by these vessels 

 differ from those which theory in its strict sense would admit as being correct. 



