PHYSICAL LABORATORY AT THE UNIVERSITY OF SYDNEY. 99 



three taps with long nozzles, the latter varying from one to five- 

 eighths of an inch in diameter. Tlie valves employed throughout 

 are Peat's Patent — and are admirable when in good order — cai-e 

 has to be taken however to test them — especially the smaller sizes, 

 as small defects in workmanship tend to cause dripping. This is a 

 pity because the principle of these valves is excellent — in fact I 

 know of no reason why any other foi'm of tap should be tight ; 

 though some of them cei'tainly are. The great advantage of a screw 

 valve is that the regulation is very perfect, that there is no 

 throttling, and that the tap cannot be turned off suddenly ; this 

 by the way is sometimes a disadvantage. There are also two 

 quarter-inch taps above each sink for the purpose of working 

 velocity pumps. These pumps as usually made of glass are 

 generally ineffective owing to the makers being apparently 

 ignorant of the principles on which they ought to work ; they 

 therefore require to be tested before they are bought. Great 

 attention has been directed to obtaining a steady water pressure ; 

 the solution finally arrived at was to lay on a six inch pipe from 

 the new Medical School tank. This gives us a pressure of about 

 thirty-five pounds per square inch and is practically quite steady 

 as nobody else uses water out of our pipe ; and the tank is so large 

 that the differences of level that occur in it are insignificant. The 

 level is kept more or less constant by a ball tap. I find that a 

 pressure gauge on the water supply is most useful ; the one I 

 have is a large Bourdon gauge and was tested by me against a 

 column of mercury ; its readings as a rule are wrong by about 

 six per cent. The system of lighting adopted in the Lecture room 

 (as in most of the large rooms) depends on the use of a single sun 

 light arranged to act as a ventilator ; triple wall brackets carrrying 

 both gas and electric light ; and a gas and electric border over the 

 lecture table. The electric light is all controlled by a switch 

 within reach of the lecturer ; and by switches under each group 

 of lamps. A similar remark applies to the gas as far as the sun 

 and head lights are concerned. The triple gas and electric light 

 bi'ackets have been specially designed and will it is hoped prove 

 free from the many inconveniences attending such arrangement 

 where the workmanship is bad. However the contact insulation 

 resistance for the whole installation including three hundred lights 

 and the service mains (to be referred to presently) is fixed at four 

 megohms. The work is not finished yet but is quite up to the 

 standard so far, though several bi'ackets have had to be taken out 

 and replaced. Some attention has also to be paid to the slate 

 switches. I have had them all tested by a high resistance galva- 

 nometer and megohm, and many have been rejected in consequence. 

 The rest have been baked and lacquered. This hint I owe to 

 !Mr. Russell who has long used french-polished slate, an ideal 

 base for many instruments. 



Below the projecting top of the lecture table run various pipes. 



