58 SMITHSONIAN CONTRIBUTIONS TO KNOWLBDG1 VOX,. -7 



A further difficulty experienced in the use of these boilers had been thai of 

 obtaining dry steam for the engines, as during the early experiments the steam 

 had been delivered directly into the engines from the boiler coils. Bui in A.ugus1 

 the writer devised n chamber, known as the " separator," where it had an op 



portunity to separate from I he water and issue as dry steam, or a! Leasl approxi 

 inately dry steam. This was an arrangement familiar in principle t<> steam en 

 gineers under aunt her form, 1 mi 1 it was one el' the many things which, in the igno 

 ranee of steam engineering the writer has already freely admitted, he had to 

 ivin\ enl for himself. 



At aboul the same time, a new pump was designed to drive the water from 

 the bottom of the separator, which served the double purpose of steam drum and 



rvoir, into the coils. This pump had a diameter of 4.8 cm., and was run at 

 L80 -t rokes per minute. 



The result of the firsl experiments with these improvements demonstrated 

 that, within certain limits, the anion id of water evaporated is proportional to the 

 circulation, and in this boiler the circulation was still the thing thai was at fault, 

 finally, the results of the experiments with the two stranded, triple coil boiler 

 iua\ he summed up in the statement that it was possible to maintain a pressure 

 of Sll pounds, and that witli it the engines could be made to develop from 0.3 to 



ii. I II. P. at best. II weighed 650 grammes (1.43 pounds) without the asbestos 

 jacket. 



About this time the writer had the good fortune to secure the temporary 



services of Dr. ('ail I'.arus, an accomplished physicist, with whose aid a greal 

 Variety of boilers were experimented on. 



The next form of boiler tested was that shown at N (Plate 13), made on a 

 system of coils in parallel, of which there were twenty complete turns. In the 

 first tesl it generated but 20 pounds of steam, because the (lame refused to work 

 iii the colder coils. The work of this boiler was very unsatisfactory, and it was 

 only with the -.Tea test difficulty that more than ten pounds pressure could he 

 maintained. 'There was trouble, too, with the circulation, in that when the llame 

 was in full play the pump seemed to meet, an almost solid resistance, so that it 

 could not be made to do its work. 



A new boiler was accordingly made, consisting of three coils of four strands 



each. With this the pump worked easily, lull whereas it was expected to gel 120 



pounds pressure, the besl that could lie obtained was 7<> pounds. The outer 



coil was then stripped oil', and a trial made in which everything ran smoothly 



and Hie pressure mounted momentarily to 90 pounds. After some adjustment, 



a mean pressure of 80 pounds was obtained, giving 730 revolutions of the en 

 gine per minute, witli an indicated horse power of (l. .".'J. 



ft was shown in this work that, within certain limits, steam is generated 



most rapidly when it is used most rapidly, so that two engines could be used 



