270 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1912. 



or mass of refractory fragments a mixture of air and gas in the pro- 

 portion to assure perfect combustion and which must be discharged 

 fast enough to prevent the flame "striking back." The gas is ignited 

 as it flows out of this contrivance. 



In the ordinary Bono heater, based upon this principle, the ordi- 

 nary boiler tubes are replaced with ones filled with pebbles. The 

 combustion takes place within the first 150 millimeters of the tubes 

 and the burnt gases raise the pebbles to incandescence. The 

 experiments made at Yorkshire gave encouraging results. The 

 experunental heater proved very active and easy to regulate. 



I wrote at considerable length in the Review for 1909 on the sub- 

 ject of superheaters. The idea of superheating steam in order to 

 avoid harmful condensations appears to have originated with a 

 mechanician of Strasburg named Becker, who in 1827 obtained 

 a patent for that purpose, and it is rather remarkable that since 

 then it has been in Alsace, where the practical realization of super- 

 heating has taken place. It was at Logelbach that Hirn, in his 

 famous experiments, made with two engines of more than 100 

 horsepower, showed that economies of more than 20 to 25 per cent 

 could be obtained by superheating less than 100°. Schwoerer, for 

 a long while secretary to Birn, has continued the researches of his 

 former master and triumphed over the difficulties v.'hich retarded 

 the practical application of superheating. In 1904 he announced at 

 the Societe d'Encouragement pour Flndustrie nationale that during 

 the last 10 years he had built more than 5,000 superheaters of his 

 design and still continued with the same success. Schwoerer's 

 apparatus consists of a set of very thick, straight tubes, about 3 

 meters long, with exterior transverse thickenings and longitudinal 

 interior ribs, assembled in a semicircular frame. Its weight is about 

 300 kilograms per meter. The device is sometimes used horizontally, 

 sometimes vertically. The great mass of metal serves as a reservoir 

 of heat. 



Davane, in a memoii- published in the Bulletin du Congres inter- 

 national des Chemins de fer (1909), told of the employment of 

 superheatmg in locomotives and gave many interesting data. The 

 ■f ollowhig are a few of his conclusions : The economy is inappreciable 

 for a superheating of 30"^ to 40°. The temperature of the superheated 

 vapor must not bo raised above 350°. Under such conditions 

 economies reacliing from 20 to 22 per cent may be obtained. The 

 saw-tooth profile of the roads (that is, frequent changes from up to 

 down grade), the many and prolonged stops at stations, are very 

 unfavorable to the use of superheating on locomotives. The increase 

 of power is obtamed only on certam lines. The great superheating 

 necessitates the proper protection of the cylinders and the distributing 

 system as well as special lubrication with oils suitably chosen. 



