282 



VENTILATION. 



fixed roof, reaching from the front wall 

 to the back ; b represents one of the small 

 ventilators in the front wall ; c c one of 

 the small ventilators at the top of the 

 back wall, to allow the heated air to 

 escape. These small openings, with the 

 addition, sometimes, of one or two in the 

 ends, are all the means available for re- 

 ducing the temperature in a hot summer 

 day. If such houses had been heavy 

 wooden ones, affording ten times as much 

 shade, they would doubtless have had ten 

 times more space for ventilation. Suppos- 

 ing, then, that the house is built and filled 

 with plants, if this happens to be late in 

 autumn, they will look remarkably well 

 in winter and early spring ; but as soon 

 as the sun's rays become more perpendi- 

 cular, shining in a clear sky for a few 

 days, the worst effects are produced. The 

 change is easily explained. These struc- 

 tures are so light, that they admit nearly 

 all the sun's rays. The atmosphere is 

 thus subjected to sudden variations of 

 temperature, although every ventilating 

 space be open ; and the moisture is drawn 

 from the leaves of the plants much faster 

 than their roots can supply them ; con- 

 sequently the leaves flag, curl at their 

 edges, and ultimately become sick and 

 unhealthy. That this is a correct expla- 

 nation, is proved by the fact that succu- 

 lent plants, such as cacti, having leaves 

 with fine evaporating pores, will thrive in 

 a house of this description. The front 

 ventilators in such houses are placed in a 

 very good situation for the admission of 

 air ; but those in the back wall are in a 

 very bad one for allowing it to escape 

 when it is overheated. Some persons 

 lately had rather an expensive example 

 of the truth of this principle in the work- 

 ing of a new method of heating, when it 

 was supposed that, if the pipes were placed 

 in a chamber below the level of the floor of 

 the house, and communicating with it by 

 a few holes* or trunks made along the 

 front or back, the heat generated by the 

 pipes in the chamber would all ascend 

 through these places and keep up a suffi- 

 cient temperature. Such, however, was 

 not the case ; a great quantity of heat re- 

 mained where it was, and the plants were 

 in some instances frozen. So in like manner 

 the heated air passesout very slowly at these 

 back ventilators, and the plants are burned. 

 " A house, of which the following is a 



section, fig. 373, would have all the ad- 

 vantages of the other with regard to 

 light, and, at the same time, the means 

 of sufficient ventilation would be provided. 

 a represents the ventilating boards in the 

 front wall, as shown in the last section : 



Fig. 373. 



these could be 

 used in mid- 

 winter, when 

 the air thus ad- 

 mitted would 

 have to pass 

 over the hot- 

 water pipes, b, 

 before it came 

 in contact with 

 the plants; c is 

 a glazed ventilator, as seen in common 

 wooden houses ; and<i are ventilators in the 

 roof, which move on hinges. The span- 

 roofed curvilinear house is not liable to such 

 sudden variations of temperature, because, 

 having glass on both sides, many of the 

 rays pass through, and therefore they are 

 much cooler than those which have a 

 back wall. The annexed sketch, fig. 374, 



Fig. 374. 



shows a house of this description, which 

 is ventilated at the base in the same man- 

 ner as the preceding, and at the top, by 

 either having part of the roof of an in- 

 clined plane with movable sashes, a a, or 

 by leaving a considerable space below the 

 coping, and fixing wooden ventilators on 

 it. Having pointed out what I consider 

 to be defective in the construction of 

 many of these houses, other, and perhaps 

 better, methods of remedying these defects 

 may be suggested. The inclined plane 

 and sliding sashes might be used in the 

 first section, instead of the hinged venti- 

 lators, if it is thought desirable. It 

 would be rather advantageous than other- 

 wise with regard to light, being of course 



