ill the Medical Department of the University of Pennsylvania A^l 



The canopy over the hearth is nearly covered with shelves 

 for apparatus, which will bear exposure to air and dust, espe- 

 cially glass. In the centre of the hearth there is a stack of 

 brick-work for a blast-furnace, the blast being produced by 

 means of very large bellows situated under one of the arches 

 supporting the hearth. The bellows are wrought by means 

 of the lever, represented in the engraving, and a rod descend- 

 ing from it, through a circular opening in the masonry. 



There are two other stacks of brick-work on the hearth 

 against the wall. In one there is a coal grate which heats a 

 flat sand-bath ; in the other there is a similar grate for heating 

 two circular sand-baths, or an alembic. In this stack there is 

 likewise a powerful air-furnace. In both of the stacks last- 

 mentioned there are evaporating ovens. 



The laboratory is heated not only by one or both of the 

 grates already mentioned, but also by stoves in the arches be- 

 neath the hearth ; one of these is included in a chamber of 

 brick-work. The chamber receives a supply of fresh air 

 through a flue terminating in an aperture in the external wall 

 of the building; and the air after being heated passes into 

 the laboratory at fifteen apertures, distributed over a space 

 of thirty feet. Twelve of these apertures are in front of the 

 table, being four inches square, covered by punched sheet iron. 

 In the hearth there is one large aperture of about twelve by 

 eighteen, covered by a cast-iron plate full of holes, the rest 

 are under the table. By these means the hot air is, at its en- 

 trance, so much diluted with the air of the room, that an un- 

 usually equable temperature is produced, there being rarely 

 a difference of more than two degrees of Fahrenheit between 

 the temperature in the upper, and in the lower part of the 

 lecture-room. There are some smaller windows to the south, 

 besides those represented in the engraving. One of these is 

 in the upper story, from which the rays enter at the square 

 aperture in the ceiling over the table on the right. Besides 

 these, are the windows represented'in the engraving at the back 

 of the hearth, and four others in the apartments to the north of 

 the gallery. All the windows have shutters, so constructed 

 as to be closed and opened with facility. Those which belong 

 to the principal windows are hung like sashes with weights, 

 so that they ascend as soon as loosened ; and when the light 

 is again to be admitted, are easily pulled down by coi ds, and 

 fastened. In addition to the accommodation already men- 

 tioned, there is a large irregular room under the floor of the 

 lecture-room on the eastern side. This is used as a place to 

 stow a number of cumbrous and unsightly articles, which are, 

 3 1 '2 nevertheless, 



