186 Proceedings of the 



February 19 th. 



Mr. Ainger, in a notice on the * Economy of the Steam Engine/ 

 alluded to the misapprehensions which had at various times existed, 

 as to the saving of fuel which would result from substituting ether 

 or alcohol for water, as the vaporizable material ; and he endea- 

 voured to show, that a very simple calculation applied to the known 

 facts, in regard to those substances and their vapours, would have 

 prevented those misapprehensions, and would, indeed, have fur- 

 nished the same results as have been obtained from experiment. 

 The reasons usually assigned for proposing to use these liquids 

 instead of water, have been the lower temperature at which they 

 assume the state of vapour of a given elastic force (alcohol, for 

 instance, boiling at about 170°, and ether at about 100°) ; and, also, 

 the smaller latent heats of their vapours, as compared with steam. 

 The boiling point of a liquid, and the latent heat of its vapour, form, 

 however, only a small part of the consideration required for calcu- 

 lating its economy. The cost of a certain quantity of force derived 

 from a given bulk of liquid, depends on the boiling temperature, 

 the specific gravity, and the specific heat of the liquid, and, on the 

 latent heat, the actual weight, and the specific gravity of the vapour. 

 These being known, the relative costs of a certain quantity of power 

 derived from two or more liquids may easily be deduced, as in the 

 following comparison between water, alcohol, and ether. 



It may be assumed, that these substances are all supplied to the 

 engineer at the same temperature, say 50°. To raise them to their 

 boiling points, they will require the following additions : 



Boiling Point. 



Water . . 212 - 50 = 162 

 Alcohol * 170 - 50 = 120 

 Ether . . 100 — 50 == 50 

 Multiply these numbers by the specific gravities of the liquids, 

 respectively. 



Specific Gravity. 



162 X 1000 == 162,000 



120 X 800 = 96,000 



50 X 740 = 37,000 



These results would require to be multiplied by the specific heats 

 of the three liquids ; but, as the specific heats are not very perfectly 

 ascertained, and, as far as they are known, do not appear to differ 

 very considerably ; and, further, as the cost of heating the liquid 



