MECHANICS AND USEFUL ARTS. 67 



IMPROVEMENTS IN THE MANUFACTURE OF GAS. 



Mr. Leslie, a well-known gas engineer of London, proposes to econ- 

 omize the process of gas-making by making it two distinct operations, to 

 be carried on in different localities. The first operation he proposes 

 should be carried on in the immediate vicinity of the mines, where 

 coal is cheap, labor plentiful, and an acre or two, more or less, cov- 

 ered by the works, of little consequence. Here the coal is to be sub- 

 mitted to distillation in the simplest manner, and the product collected 

 in the form of coal-oils ; the oil so obtained may then be submitted 

 to purification from the nitrogenous and sulphur compounds which 

 are so fruitful a source of complaint when they find their way into 

 illuminating gas ; it being far easier and cheaper, according to Mr. 

 Leslie, to remove all the nitrogen and sulphur from a gallon of coal- 

 oil, than from the one hundred and fifty or two hundred feet of gas 

 of which it is the representative. When the oil has been properly 

 prepared, and purified from all deleterious substances, Mr. Leslie pro- 

 poses that it should be conveyed to the place where it is needed, 

 and there converted into gas. The works necessary for this purpose 

 need only consist of a few retorts and a gas-holder or two ; all the 

 complicated machinery now needed for the purification being rendered 

 unnecessary. The retort being heated to redness, a little of the oil 

 is allowed to flow into it, when instantly it is converted into perma- 

 nent gas, and carried through a pipe into the gas-holder of the ordinary 

 construction, from which the illuminating gas is supplied to the mains 

 as heretofore. Mr. Leslie calculates that a ton of good coal will 

 yield one hundred and sixty-eight gallons of the hydro-carbon fluid. 

 Now one hundred and sixty-eight gallons is almost exactly one cubic 

 yard, and as each gallon is estimated to yield almost instantaneously 

 one hundred and twenty-eight cubic feet of gas, we have thus twenty- 

 one thousand five hundred and four cubic feet of gas from one hundred 

 and sixty-eight gallons, the material for the production of which only 

 occupies the space of one cubic yard. 



The adoption of this plan, Mr. Leslie urges, would render unneces- 

 sary the carriage to metropolitan gas-works of an immense quantity 

 of useless material, in addition to the real gas-making constituent of 

 the coal, and also render it unnecessary for gas companies to have 

 large and expensive works in cities, where the process of purification, 

 with its concomitant evil of half poisoning the neighborhood by the 

 sickening odor with which they are surrounded, is obliged to be car- 

 ried on. 



DRESSER'S PROCESS OF NATURE-PRINTING. 



The London Art Journal for July, 1861, gives the following descrip- 

 tion of a new process of " nature printing," devised by a Dr. Dresser, 

 an Englishman. 



The process is one by which images of foliage may be taken by 

 any who have leisure, and choose to devote an hour or two to the regis- 

 tration of the beautiful forms of our leaves. The process, by its sim- 

 plicity, commends itself, and the results gained are of the most charm- 

 ing character. The Vienna process of " nature-printing " has achieved 



