394 
PROFESSOR O. REYNOLDS AND MR. W. II. MOORBY 
tions to the preliminary reduction of all subsequent trials. These included the 
provision of the hand brake, by means of which the engine speed on starting and 
finishing the trials could be easily eontrolled, and the observations of the speed of 
the engine and the temperature of the brake which were taken at the moments of 
starting and ending the trials. 
j\-gain, the teiminal corrections and other incidental errors had very unequal 
weights when acting on the quantities obtained in the hour light trials and in the 
half-houi heavy tiials which latter quantities required doubling before the subtrac¬ 
tion requisite to eliminate losses of heat could be effected. 
It was, therefore, decided that in future all trials should be of equal duration 
(viz. 62 minutes), and this necessitated the immediate careful checking of the scale 
of tlie weighing machine, which was thereupon proceeded with. Furthermore, it was 
probable that many of the discrepancies which occurred were due to the small 
quantities of water it was possible to deal with at the low speeds hitherto used, and 
to remedy this defect a larger amount of work was done and heat generated by 
increasing the speed in all the recorded trials to 300 revolutions per minute. 
Incidentally this increase of speed was conducive to the steadier runnino- of the 
engine. 
I was much troubled wnth bubbles of steam in the discharge pipe, and to prevent 
their formation the rising pipe was lengthened till it gave a head of 11'3 feet over 
the thermometer bulb. 
These trials also furnished information wdiich led to the adoption of a pressure of 
9 inches of mercury in the artificial atmosphere. It was found that wu'th IfioFer 
pressures than this the air by some means found its way into the discharge pipe, even 
with the lengthened rising pipe in position. 
During the first few trials the only regulation of the water supplied to the bearings 
of the brake consisted of screw clips on the rubber pipes carrying the wnrter. These 
wmie found to be vep^ inefficient, and two cocks were substituted, each of wdiich 
carried a scale which showed the amount to which it wms open at any time. 
34. Before dealing with the tables showdng the final reduction of the experiments 
made, it is necessary to mention a preliminary reduction of trials Nos. 1 to 42 shown 
in Table A (p. 413), from wdiich the constants used in the determination of the losses 
of heat by conduction along the shaft, and also by radiation, wmre deduced. 
In this table the actual observations are as far as possible omitted, since they wdll 
appear la,ter in the completely reduced tables. 
It wull be seen that the table consists of fliree similar parts, referring respectively 
to the heavy trials, the light trials, and the differences. 
In eacli pa,rt 
naiy wmy. 
Col. 1 gives the number of the trial. 
Col. 2 gives the wmrk done, calculated in the ordi 
