Laboratory at St. Johns College, Oxford. 219 



The arrangement of the surface condenser serves the double 

 purpose of avoiding scale in the boiler (the Oxford water being 

 heavily charged with lime) and of economizing steam, by let- 

 ting the condensed water be pumped into the boiler again at a 

 high temperature. The Willan's engine is not economical in 

 steam; and its power is greater than is required for the main 

 purposes of the laboratory. It answers fairly for the original 

 purpose of blowing the bellows : and very well for such pur- 

 poses as grinding tools and cutting the teeth of wheels on 

 the lathe, particularly the latter, which is heavy work. But 

 I have come to the conclusion that it is a mistake to have 

 the motor in the room at all when acoustic experiments are 

 being carried on. There is always some noise. In the case 

 of a similar arrangement being fitted up again, it should be 

 regarded as almost a necessity to have a separate room, or, if 

 possible, a separate building, for the motor ; and then a gas- 

 engine would be admissible. This is out of the question in the 

 same room, on account of the noise. 



On another occasion, however, in publishing the results of 

 the first investigations made in the laboratory, I shall show 

 that results have been obtained with the combination of engine 

 and bellows as originally designed. In all cases in which very 

 minute analysis by the unassisted ear is not involved, this 

 combination is quite satisfactory. 



The exhaust-steam pipe is fitted with a three-way cock just 

 above the condenser, from which a direct exhaust is led into 

 the chimney, so that the system can be worked as a high- 

 pressure or condensing arrangement at will. But the con- 

 densing arrangement is always used by preference, as being 

 both more economical of steam and more quiet. The high- 

 pressure exhaust causes a slight hum in the chimney, which, 

 though hardly observable under ordinary circumstances, inter- 

 feres to some extent with acoustic observations. No puffing- 

 is observed from outside with the high-pressure exhaust ; only 

 a light cloud of escaping steam rises from the chimney. 



The engine was got into position about the beginning of 

 April. The arrangements of the gas-furnace and condenser, 

 however, were very imperfectly finished by the makers in the 

 first instance ; and it was not until the middle of June in the 

 present year, after all these things had been subjected to a 

 thorough revision, that the whole arrangement could be said 

 to be in working order. A few days after the condenser was 

 put right (it had been left so that the water ran through the 

 joints of the tubes like a sieve) I had the pleasure of showing 

 to Prof. Wiedemann the combination of steam-engine and 

 pneumatic bellows, -with self-acting control of the steam-engine 



R2 



