320 THE SCIENTIFIC PAPERS OF 



much surprised if it did not prove the cheapest mode of transit in 

 London and other large towns. 



The only other point of interest to which he would allude was 

 the blowing apparatus. This was now working occasionally at 

 the Post Office in the way of trial against the engines. It was 

 not quite equal in steam economy with the engines, but it must be 

 borne in mind that the steam pressure was only 35 Ibs. or 40 Ibs., 

 and the steam engine employed was a very good one. Com- 

 parative trials showed that, with the same boiler power, the steam 

 engine maintained from 2 to 8 inches more vacuum with the tube 

 open than the steam blower ; but other experiments with a higher 

 pressure of steam reversed that result. With steam of 70 Ibs. 

 pressure, the working results of the steam blower were superior to 

 those of the steam engine. 



Mr. Hatvlcshaiv, Past-President, inquired how the risk of cutting 

 the carrier in two by the introduction of the rocking-frame was 

 avoided, supposing it was just passing the joint at the moment 

 the rocking frame was worked ? 



Mr. Siemens replied, that the attendant heard when the carrier 

 had arrived, as it made a little noise ; but a small bell might be 

 made to sound automatically when the carrier had arrived within 

 20 yards of the station. 



In the discussion of the Paper 



"ON THE ABA-EL-WAKF SUGAR FACTORY, UPPER 

 EGYPT," by WILLIAM ANDERSON, M. Inst. C.E., 



MR. C. W. SIEMENS * said the paper dealt with two separate 

 subjects, one of a mechanical, and the other of a chemical 

 character. It appeared to him that the author had very satis- 

 factorily solved the mechanical questions involved. The arrange- 

 ments of the mill-gearing had evidently proved successful, but it 



* Excerpt Minutes of Proceedings of the Institution of Civil Engineers, Vol. 

 XXXV. Session 1872-73, pp. 75-78. . . 



