MISCELLANEOUS. 91 1 



60 working places. No. 2 (Fig. 1) is arranged for the advanced or quantita- 

 tive students, and contains ten blocks of four benches, each for the accommo- 

 dation of 40 students. 



The first essential in a laboratory, that of good light, is provided for by 

 large windows and skylights on both sides. The other essential, that of 

 plenty of ;air and good ventilation, is secured by lofty rooms having cubic 

 contents of upwards of 50,000 ft., and by means of the powerful draught of a 

 high cbininey at one end of the laboratory block ; the upward current being 

 maintained by means of a furnace in the basement at the foot of the chimney, 

 which furnace in the winter works the hot water heating apparatus, and in 

 the summer simply serves for ventilating purposes. 



The ventilation of the laboratory may be divided into two kinds, (a) the 

 general ventilation, and (6.) the special ventilation, (a) The general venti- 

 lation is effected by a wooden perforated ceiling running the whole length 

 of both of the main laboratories, and conveying the vitiated air by a large 

 air-trunk to the shaft, within which rises the smoke flue of the furnace. 

 The supply of fresh air is obtained from a high level by a fresh air shaft, 

 down which the air passes, the hot water pipes being drawn by the aspiration 

 of the chimney into the laboratories through gratings placed in the walls. 

 This ventilation acts so successfully, that although no less than 44 beginners 

 are now working in the qualitative (No. 1) laboratory, and 42 advanced 

 students are working in the quantitative (No. 2) laboratory, still the air in 

 both rooms is clear and pleasant throughout the day. In case, through 

 negligence or accident, a large escape of acid fumes should occur, the 

 windows being hung on pivpts, can all be opened, and a thorough renewal 

 of the air be effected in a few minutes. (6) The special ventilation is also 

 worked by the main shaft, and is divided between the evaporating niches 

 in the walls shown in plan, and in detail in Figs. 13 to 21, and the sul- 

 phuretted hydrogen closets marked A in the detailed drawing on each 

 working table. Each of the niches is provided with an upright glazed 

 earthenware pipe, 4 in. in diameter, running into a horizontal pipe of the 

 same material, 12 inches in diameter, communicating directly with the main 

 chimney, the draught in which is powerful enough to draw air from each 

 one of the niches without the necessity of any gas flame being used for 

 aspiration, and no escape is noticed in the working of these when any fumes, 

 even of sulphuric acid, are evaporated in any quantity.. In order to prevent 

 the condensation of acid liquors, or of water, when these substances are 

 boiled in the niches, a porcelain funnel is introduced into the lower part of 

 the earthenware pipe inside the niche ; all vapours generated under this funnel 

 are immediately swept into the chimney, and no condensation whatever takes 

 place inside the glass windows of the niche. One of these porcelain funnels 

 is placed in the exhibition. The amount of air which in actual practice is 

 found to pass up these draughts, is as follows : 



The large niches at the west end of the laboratory, aspirate 100 cubic ft. 

 of air per minute, and each of the smaller ones in the three walls running 

 east and west, 12 cubic ft. of air per minute. 



The sulphuretted hydrogen closets in each working bench, shown in section 

 in Fig. 11, and in plan in Figs. 7 and 9, are joined together in groups of two or 

 four, and placed in connexion with a 7 in. or 4| in. glazed earthenware pipe 

 communicating with a horizontal flue shown in section in Fig. 5, running 

 between the fireproof arching under the floor, and passing into the chimney 

 at the point (S), Fig. 1. The down draught in each of these closets is con- 

 tinuous and powerful, each closet in the laboratory No. 1 aspirating at the 

 rate of 5 cubic ft. per minute, whilst those in laboratory No. 2 aspirate on an 

 average 20 cubic ft. per minute, those at the furthest end of the laboratory 

 differing but slightly from those situated nearest to the chimney. -The details 



