]Q2 APPLICATION OF THE GAS FROM COAL. 



For a longer V/heii the gas is applied to lighting the streets by night- 

 Yourable' '^' ^lovvever, perhaps we may state tlie time at an average as 

 ten hours a day ; and the longer the time, as Mr. Murdoch 

 justly observes, the greater will be the balance in favour of 

 the gas, since the apparatus will remain nearly the same. 

 But various fie- But then, there are several circumstances farther to be taken 

 b '^I'ade "^"'' ^"^® consideration. Though the greater part of the appara- 

 tus would not be altered, it appears an increase of some 

 parts would be necessary, if the burning were to be conti- 

 nued beyond three liours. We must add too to the expen- 

 diture, the rent of houses in every part of the town for 

 holding the furnaces and ap[)aratus, the wages of persons 

 to attend these, and the salaries of clerks, none of which 

 were necessary in Mr. Murdoch's case. Besides, the price 

 of coal must probably be increased by the additional con- 

 sumption, and that of coak would certainly fall very greatly, 

 from the quantity produced beyond the demand for it. The 

 estimate too must be made in comparison with common 

 lamp oil, the expense of which may be reckoned at not 

 more than two thirds the cost of candles. Farther, the gas 

 lights are said to give double the light of the common street 

 lamps, and this is certainly an accommodation to the pub- 

 lic : but then, as the calculation of Mr. Murdoch is found- 

 ed very properly on the quantity of light given, this will 

 affect the estimate in a similar ratio, so that the expense of 

 the oil must be diminished by one half. On these grounds 

 the estimate would appear somewhat in the following formj 

 taking it at an average of ten hours every night. 



Estimate with- 550 tons of cannel coal £2200 



out these de- OQO tons of common coal 45O 



Interest of capital, and wear and tear of appa- 



tus 800 



3450 

 Deduct for 350 tons of coak 875 



2575. 

 The expense of lighting to an equal extent with oil, ac- 

 cording to the estimation above give , wo>dd £3333. It 

 j;^nst be observed, nothing is here allowed for the coal-tar, 



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