HEATING GREENHOUSES. 199 



well to stud}' the work of Professor Tyndall ou heat. He is the 

 best autborit}', and bis experiments can be tried by anybody. 



Mr. Woodford said that Mr. Zirngiebel's bouses were the first 

 he ever saw heated under pressure. He has four houses heated by 

 one boiler, the expansion-pipe being a hundred feet from the 

 boiler. Tlie furnace is like that recommended in the essa}', though 

 he could not say about the partition, but it has a coil of pipe, like 

 a beehive, on top. An arm runs to each of the four houses, and 

 they are heated better than any others of his houses. The whole 

 of the water in them moves. He has a ventilator, which he opens, 

 so that the chimney is cold. The speaker could not understand 

 why the two lower pipes in the plan proposed by him should be 

 cold. In this plan the furnace fire goes up and afterwards down. 



William C. Strong thought that the use of steam would be more 

 general in future, especially in large establishments where several 

 houses are to be heated from one fire. 



William D. Philbrick reraaiked that there seemed to be some 

 confusion of ideas with some of the speakers in regard to the use 

 of pressure in hot water circulation ; its only advantage is in the 

 higher temperature which can be given to the pipes ; it does not 

 render friction less or circulation more rapid, and is objectionable 

 on account of the greater difficulty in keeping the pipes tight. If 

 pressure is used, there must be a safety-valve on the stand-pipe or . 

 elsewhere. It is possible, under high draugliton a windy night, for 

 the water to boil over and be thrown out, so as to leave the upper 

 part of the circulating pipes full of air and steam, which would 

 obstruct the circulation. If he wanted pressure he would prefer 

 steam. Mr. Hill's apparatus works perfectly. 



Mr. Woodford spoke of the advantage of a greater quantit}^ of 

 water than is found in steam pipes. 



Col. Wilson said that this advantage would not exist if the ar- 

 rangements were properly made. Mr . Hill's house was kept at a 

 temperature of 40° when the thermometer outside showed 15° be- 

 low zero. The adjustment is simple and automatic, a variation 

 of one ounce per square inch in the pressure changing the regula- 

 tor ; and it obviates the objections previousl}' made against steam. 

 The speaker knows you can send ten times the heat through 

 pipes with steam that 3'ou can with water. 



Mr. Wood said that he has a steam-heater in liis dwelling-house, 

 and though he has an automatic arrangement, he burns twice the 

 coal there that he does in his greenhouse with hot water. He 



