386 



PEOF. H. L. CALLENDAR, PREFACE TO 



elimination of errors due to variation of wetness or external heat loss. The apparatus 

 is shown diagrammatically in fig. 2. The calorimeters were made of very thin steel 

 tube, and each was well lagged and drained, and doubly jacketed with its own 

 exhaust, so that a steady state was reached within five minutes of turning on the 

 steam. The throttle tubes were made interchangeable, so that the external loss could 

 be determined by using throttles of different sizes simultaneously in the two 

 calorimeters. The elimination of the heat-loss, in the usual method of employing the 

 differential instrument with equal throttles, proved to be nearly perfect, but the 

 observations were very useful in correcting the previous results with the single 

 calorimeter. The apparatus was completed early in July, 1897, and was exhibited to 



SUPPLY 



GAUGE P n 



II! 



THROTTLES 



Fig. 2. 



several members of the British Association on the occasion of their visit to McGill 

 College in August. But owing to pressure of other work the results could not be 

 completed in time for the meeting at Toronto. About thirty observations were taken 

 by Prof. NICOLSON and myself during the vacation, which were supplemented 

 by others taken by the Senior Demonstrator, Mr. H. M. JAQUAYS, and the fourth 

 year students during the ensuing session. These confirmed the previous conclusions, 

 but the work was unfortunately interrupted, before any observations had been 

 obtained at temperatures above 180 C. or pressures above 130 Ibs., by the unexpected 

 translation of Prof. NICOLSON and myself to posts in England early in 1898. 

 Prof. NICOLSON intended to set up a duplicate of the apparatus at Manchester as soon 

 as possible, while I continued the investigation at University College. But facilities 



