612 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



1,000,000 is used for kelp and green manuring. It is proposed to dry it by 

 the process for burning "wet fuel," by which the weed itself will furnish 

 nearly all the requisite heat. 



Surface Condensers. 



The selected subject for discussion, "Surface Condensers," was then 

 taken up. The Chairman said that in the two previous discussions on this 

 subject, all the novel and prominent features of this kind of condensing 

 apparatus, as applied to low pressure steamers, had been fully illustrated; 

 it only remained to examine those which have been used on high pressure 

 engines, and to investigate more clearly the causes which are said to destroy 

 very rapidly the boilers supplying steam to such engines. 



Mr. Bartlett proceeded to briefly describe the arrangements used for sur- 

 face condensation in high pressure steamers — not for the purpose of pro- 

 ducing a vacuum, but only when it is quite important to use, during com- 

 paratively short voyages, fresh water in the boilers. Such condensers, in 

 several government vessels lately constructed to navigate shallow waters, 

 consist merely of tubes running outside of the vessel, near the bottom. 

 They are properly protected from injury, but are in direct contact with the 

 ■water, which is changed by the progress of the vessel, so that condensation 

 is effected without pumping into the vessel cold water. 



Mr. Root explained the construction of a surface condenser for high pres- 

 sure engines, the essential characteristic of which is the use of a compara- 

 tively small surface, which is kept cold by dashing against its outside a 

 powerful stream of water. 



Mr. Stetson explained the principles on which several inventions in this 

 line had been based, of allowing a portion of the steam to blow out through 

 the condenser, or through a suitable passage, and condensing only the 

 remainder. It was of course inapplicable to the great mass of merchant 

 steamers on the Atlantic coast, and regular seagoing steamships as usiially 

 constructed, because in such the expansion of the steam was generally 

 carried to such an extent in the cylinder, that at the end of the stroke the 

 pressure was below that of the external air. But on the western rivers, 

 and on many of the recent varieties of sea-going craft, when high steam 

 is can-ied, and only a small degree of expansion used, the steam is dis- 

 charged at above atmospheric pressure. If this steam is taken entirely 

 into a condenser, whether jet or surface, it will require more cold water to 

 condense it than if all the surplus above atmospheric pressure were allowed 

 to escape uncondensed, and the remainder treated in the usual manner 

 Mr. Joshua Lowe, an inventor, well known in connection with pressure- 

 gauges, had an engine running in this city, near the foot of Delancey street, 

 in 1852, with an ingenious provision of this kind, but it was objectionable 

 by reason of the noise, caused by the violent closing of its self-acting 

 valves. The patent office had evidently been ignorant of this, and several 

 other experiments, because a patent had been issued within a few years, 

 seeming to cover that general mode of operating. The patent never would 

 have been sustained on such a broad construction, and he considered the 

 field open to inventors. All the efforts down to the present time at improve- 

 ment, had proved abortive. 



