Oil Gas. — Specific Gravili/. 69 



implies a defection of principle: and when the almost universal 

 employment of steam as a mechanical agent in Great Britain 

 is considered, it cannot but excite every man's surprise, that 

 so important a principle as absolute safety should have been so 

 long unheeded by our engineers** 

 I am, sir. 



Your most obedient and humble servant, 

 To Dr. Tilloch. S. Leet. 



OIL GAS. 



The Quarterly Journal of Science announces that Mr. Wil- 

 son proposes obtaining this gas, by introducing the seeds which 

 contain oil into the retorts. The editors very properly add, 

 liowever, that they greatly doubt the plausibility of this pro- 

 posal; and it appears to us, to be an example of retrograding 

 in ])hysical science. 



One of the great merits of Taylor and Martineau's appara- 

 tus for producing oil gas, as now perfected by them, is its small 

 bulk compared with its power of production, and the facility 

 with which the oil may be supplied to the retort in graduated 

 quantities, and so of maintaining or stopping the supply of 

 gas at pleasure. By this, also, decomposition is effected by tlie 

 smallest possible quantity of fuel ; for the retort being once 

 made slightly red hot is easily kept so, while the oil enters it 

 only drop by drop, and being completely brought into contact 

 with the heated matter, the operation is as complete as 

 possible. 



Now, instead of this, it is proposed to adopt a plan which 

 requires that the whole charge of a very bulky material should 

 be put into the retort at once, and wherein the oil, which is 

 the only part that can produce a good gas, is so enveloped 

 by matter which is a bad conductor of lieat, that one can 

 hardly imagine how it is to be efficiently decomposed, unless 

 such a fire be employed as will reciuire large supplies of fuel, 

 and occasion a rapid destruction of the retorts. 



SPECIFIC GRAVITY. 



Mr. Creighton has communicated to the Editor of the 

 Quarterly Journal of Science, a notice of a very simple and in- 

 genious instrument for determining the specific gravities ol 

 solid bodies. 



* Our corrcsponilcnt, Mr. Lcct, is not fully informed on the subject of 

 the safety vuivc. Tliis is no longer a desiderntiini in niechamcal science; 

 hut the controul of the eaj;ine must l)elon(,' to some one: and if both miister 

 and servant be i{;norant of its nature, no steam valve, however constructed, 

 can give them knowledgt;. — Kurr. 



