1 6 THE SCIENTIFIC PAPERS OF 



produce a vacuum. An arrangement of this description, although 

 simple, is at least very imperfect ; because it is a matter of 

 considerable difficulty so to proportion the injection of cold water 

 that the first rush of steam may not forthwith be condensed, but 

 may exert its expansive force in a cold vessel, and yet that an 

 instant afterwards a complete condensation of the remaining steam 

 may be effected. If too much water be used, the air and water 

 will not be expelled, and consequently no vacuum will be formed ; 

 if too little, no final condensation will take place. The quantity of 

 injection water must be very large, because the whole of the steam 

 has to be condensed ; and having to complete the condensation in 

 the same vessel, the water must leave it at a low temperature. 



The principle of the regenerative condenser has been carried 

 still further in the regenerative engine, which has been executed 

 on a large scale by Messrs. Fox, Henderson & Co., under the 

 superintendence of the author. In this engine the steam, after it 

 has served to propel the working piston to the end of its stroke, 

 is received into a series of consecutive chambers, from which it 

 returns to the working cylinder an indefinite number of times. 

 On a future occasion the author will be glad to bring the particu- 

 lars of this engine before the Institution. 



MR. SIEMENS, in answer to enquiries, replied that the experiment 

 at the Saltley Works, had been tried with one week's working with 

 the condenser, and then one week without it ; and the saving of fuel 

 with the condenser was at the rate of 18 per cent. The apparatus 

 with which the condenser worked was however too light, and had 

 not been made for the purpose ; also that condenser was the first 

 that had been made, and the proportions had been improved in the 

 subsequent ones. 



There was a deficiency in the supply of condensing water, which 

 sometimes interfered with the regular working of the condenser, as 

 well as the defects arising from the gearing being too light for 

 working it, and these had caused irregularities in the working of 

 the engine ; there was also a difficulty in regulating the engine as 

 a condensing engine with the present governor. The steam pressure 

 was 30 Ibs. per inch ; but a smaller supply of condensing water 

 would be sufficient if a higher pressure of steam were employed. 



As regarded its use in locomotive engines, Mr. Siemens replied 



