Royal hijlltution of Great Britain. $ I 



be entirely excluded in a moment, by lowering the moveable 

 ceiling of the lantern, by which the light enters the room 

 from above, and allowing it to reft on the cornice which 

 makes the finifh of the lower part of the lantern, juft above 

 the level of the flat part of the ceiling of the room. 



The form of the room isfemicircular,with an addition of a 

 parallelogram, equal in length to the diameter of the circular 

 part of the room (60 feet), and 15 feet wide; and there are 

 eleven rows of feats rifing one above the other below, and 

 three rows of feats in the gallery : and there is a covered cir- 

 cular paflage, eight feet wide, all round the room, without, 

 under the higher rows of feats, next the wall, and four con- 

 venient openings or vomitoria, vyith light doors with two 

 wings, which mut of themfelves without noife, forming fo 

 many paflfages of communication between the lower part of 

 the theatre or pit, and the arched gallery or paflage without. 

 The floor and feats of this theatre are painted of a dark 

 green colour; and the feats are all covered with green moreen 

 cufhions. The floor of the circular paflage without, which 

 furrounds the pit, and the flairs belonging to the vomitoria, 

 are all covered with green cloth to prevent the noife of the 

 footfteps from being heard of thofe who come in or go out 

 of the theatre during the lecture. 



The windows which form the lantern (which is 15 feet in 

 diameter) are all double, which not only renders the tempe- 

 rature of the room very equal and pleafant, but alfo prevents 

 fo effectually all noifes from without difturbing the filence 

 which reigns in the room, that even the rumbling of the car- 

 riages which pafs in the neighbouring ftreets is never heard 

 in it. 



This theatre is warmed in cold weather by fleam, which 

 coming in covered and concealed rabes, from the lower part 

 of the houfe, circulates in a large femicircular copper tube, 

 eight inches in diameter, and above 60 feet long, which is 

 concealed under the riling feats of the pit. 



Adjoining to this new theatre is the apparatus room, 

 which communicates with it by a door which is on one fide 

 of the large open chimnev fireplace within the theatre, and 

 juft behind the lecturer's table, which chimney fireplace 

 ferves for placing the furnaces that are occafionally ufed in 

 the chemical experiments. 



The repository, which is 44 feet long, and 33 feet wide, 

 (the ceiling of which, and the floor of the theatre, which is 

 above it, being fupported by two rows of handfome columns,) 

 is finished, and already contains a confiderable number of 

 fpecimens of new and ufeful mechanical contrivances. 



Vol. XIII. No. 49. F The 



