B. TERRESTRIAL PHYSICS AND METEOROLOGY. 19 



B. TERRESTRIAL PHYSICS AND METEOROLOGY. 



THERMODYNAMIC ACCELERATION AND RETARDATION 



OF STREAMS. 



In a paper by Professor Rankine, on the thermo-clynamic 

 acceleration and retardation of streams, the attempt was 

 made to prove the following principle: That in a steady 

 stream of any fluid the abstraction of heat at and near places 

 of minimum pressure, and the addition of heat at and near 

 places of maximum pressure, tend to produce acceleration ; 

 the addition of heat at and near places of minimum pressure, 

 and the abstraction of heat at and near places of maximum 

 pressure, tend to produce retardation ; in a circulating stream, 

 the quantity of energy of flow gained or lost in each complete 

 circuit is equal to the quantity of energy lost or gained in 

 the form of heat ; and in the absence of friction, the ratios 

 borne by that quantity to the heat added and the heat ab- 

 stracted (of which it is the difference) are regulated by the 

 absolute temperatures at which heat is added and abstracted, 

 agreeably to the second law of thermo-dynamics. 



Among particular cases of the thermo-dynamic acceleration 

 and retardation of streams the following were specified : Ac- 

 celeration by the addition of heat at and near a place of max- 

 imum pressure ; the draft of a furnace ; and the production of 

 disturbances in the atmosphere in regions where the ground 

 is hotter than the air. Retardation by the abstraction of 

 heat at and near a place of maximum pressure ; the dying 

 away of atmospheric disturbances in regions where the ground 

 is cooler than the air. 



Acceleration by the abstraction of heat at and near a place 

 of minimum pressure; the injector for feeding boilers, in which 

 a jet of steam, being liquefied by the abstraction of heat, is 

 enabled not only to force its way back into the boiler, but to 

 sweep a current of additional water along with it ; also, to a 

 certain extent, the ejector-condenser. 



The conduction of heat from the parts of a stream where 

 the pressure and temperature are highest to the parts of the 

 same stream where the pressure and temperature are lowest 



