BOILERS AND PIPES. 



249 



the practice of raising vapour from water 

 sprinkled on the soil, &c, which he very 

 properly condemns, and lays it down 

 as a rule, that wherever artificial heat is 

 employed, all the requisite moisture 

 should be vaporised by the heating 

 apparatus, and by it only, he goes on to 

 observe : " Various schemes have been 

 devised for this purpose, amongst which 

 may be mentioned the plan of making 

 a part of the water circulate in open 

 troughs, instead of closed pipes. This 

 plan, however, and all the modifications 

 of it, are open to the objection, that all 

 the impurities which by accident fall 

 into these troughs or gutters may be 

 carried by the circulation into the boilers, 

 and, depositing themselves there, give rise 

 to numerous unpleasant consequences. 

 A much better plan is to cast a trough 

 upon the circulating pipes, which has 

 frequently been done upon a small scale, 

 and attempted on a larger. It failed, 

 however, for some time, in consequence 

 of the tendency of any large excrescence 

 upon the pipe to bend it in the act of 

 cooling." At his sug- 

 gestion, pipes with 

 large troughs of this 

 form, fig. 332, have 

 been recently made, 

 where the troughs con- 

 tain 1 0 gallons of water 

 in each length of pipe, so that one or more 

 placed in a hothouse would furnish an 

 abundant source of moisture, without 

 abstracting it from the soil, and without 

 affecting the purity of the circulating 

 water. These troughs have the farther 

 advantage of being entirely inoperative 

 when left dry ; whereas the open gutters 

 depend on the perfectly close fitting of 

 their covers. — Vide Rogers's opinion on 

 the same subject, sect. Various Modes op 



Fig. 332. 



Heating, &c. 

 Fig. 333 



The same excellent 

 authority proposes to 

 arrange his pipes as 

 in the annexed fig. 

 333, " though," he 

 observes, " with a 

 view to the full effect 

 of the radiant heat, 

 and to the prevention 

 of any greater com- 

 munication of heat 

 to the air than is unavoidable, it would 



VOL. I. 



i 



Fig. 334. 



be better, perhaps, to expose all the pipes 

 to the plants by placing them thus, (fig. 



334,) provided the 

 height of the shelves 

 and other circum- 

 stances permitted this 

 mode of arrangement. 

 In this way a larger 

 portion of the heat 

 would arrive at the 

 plants in a radiant 

 form, because on the 

 other plan the oppos- 

 ing surfaces of the 

 adjacent pipes main- 

 tain a mutual inter- 

 change of radiation, 

 and become cooler 

 principally by the contact of the air. This 

 objection applies in some degree to the in- 

 ner sides of all pipes which are presented to 

 the wall, and from which, therefore, the 

 heat is conveyed to a large extent by the 

 atmosphere. Economy would, doubtless, 

 be consulted by closing up all those por- 

 tions of surface which are not adapted to 

 radiate directly upon the plants or upon 

 the soil. The same effect would be pro- 

 duced by clothing the inner semi-circum- 

 ferences of wall pipes with non-conduc- 

 ting materials, or, if practicable, by 

 giving to those portions a bright metallic 

 lustre." 



Glass tubes were used in the Royal 

 Gardens at Vienna so early as 1836, the 

 tubes being about 3 inches in diameter, 

 and in 3-feet lengths. The glass was 

 quite transparent, and about a quarter of 

 an inch in thickness, jointed by bands of 

 brass and cement. 



Iron pipes enamelled with glass, both 

 inside and out, are now common for con- 

 veying water for domestic purposes. Were 

 we certain that the expansion of the metal 

 when heated would not throw off this 

 glass coating, then we would say that 

 perfection had at last been reached in 

 the construction of hot- water pipes. The 

 recent invention of covering iron with 

 other metals not subject to corrosion, by 

 chemical means, may also open up a new 

 era in this department of hothouse archi- 

 tecture. 



It appears to be the fate of all newly- 

 invented improvements to meet with op- 

 position by that class of individuals who 

 are content to remain stationary, and 



2i 



