98 PROCEEDINGS OP SECTION A. 



opening into the instrument room is a long pier of brick work set 

 in cement and covered with slate. The direction of the long axis 

 of this pedestal is perpendicular to that of the lecture table ; it 

 is about thirteen inches wide and five feet long. An arc lamp is 

 permanently set up against the wall, and on the end nearest the 

 lecture table there is a galvanometer or electrometer, or both 

 together, while a suitable scale is placed above the lamp. This 

 apparatus has already worked to great satisfaction, the beam of 

 reflected light being so bright as to be very obvious to everybody 

 in the room even with all the blinds up and the room very light 

 in consequence. I tried various sorts of arc lamps and finally 

 settled on the Brockie-Pell which is noiseless and wonderfully 

 steady, and keeps the carbons for a sufficiently long period at, or 

 near, a single point. I have often used this lamp continuously 

 throughout an hour's lecture, both for tlie purpose above mentioned 

 and for optical experiments, without requiring to make any 

 re-adjustments. The lamps however are big and heavy, and 

 arrangements are being made to lift them out of tlieir boxes by 

 ropes passing round pulleys in the ceiling. It is advisable to be 

 able to adjust the lamps to diftei'ent heights in their boxes ; and 

 this is much facilitated by having them slung. It will be noticed 

 in the plan that there is a window with a shutter at the north 

 end of the lecture table. Outside on a stone slab is a permanent 

 place for a Heliostat. The shutters which are hinged each on one 

 side and fold towards the centre of the window are kept in place 

 when shut by a heavy gun-metal bar. A rectangular hole is cut 

 into each shutter from its middle edge, so that when the shutters 

 are closed we have a hole about ten inches wide and eighteen 

 inches high. By means of a frame work fitted very simply 

 inside, a slide may be caused to close the rectangular aperture. 

 Several of these slides are provided with slits, circular holes, etc., 

 and as all the shutters throughout the building are on the same 

 plan the same slides will do for all. A fireplace is provided 

 behind the lecture table long enough to hold a combustion furnace ; 

 and like all the other fireplaces fui'nished with an inch gas pipe ; 

 in addition there is a rapid water heater permanently fitted up so 

 that the noxious products of the imperfect combustion of gas in 

 this useful apparatus may go up the chimney. The sink at the 

 other end of the lecture table is one of Doulton's, with a receptacle 

 below to catch sand, mercury, etc., before the water overflows 

 into the drain. These sinks are an example of a good idea spoiled 

 by execrable workmanship. The earthenware receptacles above 

 alluded to have had to be I'emoved from every room in the 

 Laboratory and lead ones substituted, owing to the former having 

 their spouts so ill designed as to refuse to carry anything beyond 

 a mere drip of water. I refer to this in case anyone should buy 

 one of these abominations and then suffer the annoyance I have 

 had to put up with. The water sujoply over each sink consists of 



