Dr. Harems Laboratory ^ cj-c. 27 



The space partially visible to the right, is divided by a floor into 

 two apartments lighted by four windows. The lower one is employ- 

 ed to hold galvanic apparatus, the upper one for shelves, and tables, 

 for apparatus, and agents, not in daily use. In front of the floor just 

 alluded to, is a gallery for visitors. 



The canopy over the hearth is nearly covered with shelves for ap- 

 paratus, which will bear exposure to air and dust, especially 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 bel- 

 lows are wrought by means of the lever represented in the engraving, 

 and a rod descending 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 al- 

 ready mentioned, but also by stoves in the arches beneath the hearth, 

 one of these is included in a chamber of brick work. The cham- 

 ber 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 ta- 

 ble. By these means the hot air is, at its entrance, so much diluted 

 with the air of the room, that an unusually equable temperature is 

 produced, there being rarely more than two degrees of Fahrenheit 

 difference 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 back of the hearth, and four 

 others in the apartments to the north of the gallery. All the win- 

 dows have shutters, so constructed as to be closed and opened with 

 facility. Those which belong to the principal windows are hung like 



