After putting a moderate quantity of fuel in the furnace, 

 it lias been found that the engine works with full power for 

 three hours without fresh feed, and after removing the fires 

 entirely, it has frequently worked for one hour.-i^ 



The operation of the engine for an hour (under no 

 load) with only the energy stored in the brickwork of 

 the firebox attests merely to the excellence of the 

 engine's construction. However, the phenomenon of 

 an engine operating with no apparent external heat 

 supply bolstered Captain Ericsson's belief in the 

 efficacy of the regenerator. In reply to the objections 

 of one of his critics, he confirmed his belief that "the 

 regenerators are the principal heater," and that "the 

 duty of the furnace will mainly be that of supplying 

 heat lost by radiation, etc., which is no more at high 

 than low speed." ** 



Small air engines, commonly called caloric engines, 

 were built by the thousands in the latter years of the 

 19th century. These small engines were popular 

 because they would operate without feed water and 

 required little cooling water and little attention. 

 Rated by manpower rather than horsepower ("alto- 

 gether too high a standard for a Domestic Motor" ''5), 

 the engines were used for pumping water, driving 

 printing presses, and for many other tasks requiring 

 moderate power. A propeller-type cooling fan, for 

 parlor use, was powered by a caloric engine, the 

 "Lake Breeze" fan being advertised as late as 1917. *•* 

 The convenience, not the economy, made such an 

 engine popular. The following statement, which 

 appeared in the promotional literature '''' of the 

 domestic air engine, typified Captain Ericsson's ap- 

 proach to the problem of engine performance: 



In regard to the quantity of fuel required by the new motor 

 it need be only stated that in every trial made it has been 

 found but a fraction of that required by an ordinary high 

 pressure Steam Engine of equal power. Any definite state- 

 ment on this head would involve the consideration of 

 various kinds of fuel and demand a series of experiments 

 which would be as costly as useless in view of the admitted 

 great economy of the Caloric Engine. 



i^ Appletons' Mechanics' Magazine and Engineers' Journal, 1853, 

 vol. 3, p. 38. 



^ilbid., p. 121. 



*= A circular dated November 5, 1857, and signed by John B. 

 Kitching, Ericsson's financial backer for the engine in the 

 Ericsson and subsequent caloric engines, in collection of 

 Ericsson papers held by American-Swedish Historical Founda- 

 tion, Philadelphia (hereinaf"er referred to as Ericsson Papers). 



■"s Broadside, in data file, division of mechanical and civil 

 engineering. United States National Museum. 



*' Circular. See footnote 45. 



The Grand Principle 



"I am sanguine you know," wrote Captain Erics- 

 son — his enthusiasm undampened and his beliefs 

 unaltered more than a year after the caloric engine 

 of the Ericsson had been abandoned — "and therefore 

 expect confidently to succeed . . . with the dazzling 

 principle which compels metallic threads to yield 

 more force than mountains of coal." ''* These 

 metallic threads, located in the regenerator, sup- 

 posedly seized the caloric of the air being exhausted 

 and held it until it could be taken up by the incoming 

 air charge. 



This grand principle was simplicity itself, according 

 to Captain Ericsson, who said he could never under- 

 stand why so many "men of talent repeatedly com- 

 promise their reputation by putting forth statements to 

 the public, exhibiting their utter unacquaintance 

 with this all-important property of the principal 

 part of the caloric engine." " 



Caloric, he said, could be used over and over 

 again. And why not? Professor Cleghorn, at the 

 University of Edinburgh, had said in 1779 that 

 caloric was indestructible and uncreatable.* It 

 was, according to the 1819 Cyclopaedia of Abraham 

 Rees, "an elastic fluid sui generis, capable of pervading 

 with various degrees of facility, all the solid bodies 

 with which we are acquainted . . . ." The writer in 

 the Cyclopaedia explained in detail the m.eticulous 

 experiinents of Count Rumford, which seemed to 

 prove that caloric had no weight, but he dismissed 

 Rumford's work as too gross, writing: "There may be 

 an indefinite series of material substances, each a 

 million times rarer than the preceding . . . ." The 

 fact that it could not be weighed was no proof of its 

 weightlessness . ^' 



Appleton's Dictionary of Machines (1851) stated that 

 "Caloric is usually treated of as if it were a material 

 substance; but, like light and electricity, its true 

 nature has yet to be determined." 



Perhaps the oddest theory was that of a Mr. Wilder, 

 which was published in Scientific American in 1847.'- 



••s Ericsson to Messrs. Stoughton, Tyler, and Bloodgood, 

 January 16, 1855. Ericsson Papers; see footnote 45. 



■i' Applelnns' Mechanics' Magazine and Engineers' Journal, 1853, 

 vol. 3, p. 123.. 



™ Joseph H. Keenan, "Adventure in Science," Mechanical 

 Engineering, May 1958, vol. 80, pp. 79-83. 



51 Abraham Rees, Cyclopaedia, London, 1819, "Caloric.'' 



52 Vol. 3, 1847-1848, p. 449. 



52 



BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



