BOILERS AND PIPES. 



243 



evaporating pans, than by the direct 

 admission of steam from the boiler, and 

 much more gradually and permanently 

 than by pouring water on the pipes, or 

 indiscriminately syringing the house all 

 over. The idea of increasing the humi- 

 dity of hothouses is almost coeval with 

 the application of steam as a heating- 

 power. With some this practice of 

 admitting steam took its origin from an 

 idea that, if a portion of vapour was 

 thrown into the house direct from the 

 boiler or pipes, an additional degree of 

 heat would be diffused through the struc- 

 ture ; others applied it with the view of 

 destroying insects on the plants ; while 

 a few only saw the necessity of employ- 

 ing it to increase the humidity by coun- 

 teracting the drying effects of the heat 

 in the house. " The device proved, 

 at least, that gardeners began to be 

 conscious of the unnatural dryness of the 

 atmosphere of these houses, and, anxious 

 for any expedient, however unnatural, to 

 counteract it, and considering the state 

 of many plant-houses, it is not surprising 

 that its effects, as occasionally employed, 

 should, for a while at least, be apparently 

 beneficial. Food, though scalding hot, 

 and rather unwholesome, is better than 

 absolute starvation to plants as well as 

 men ; but, nevertheless, it is my firm 

 conviction that steam is invariably inju- 

 rious in a greater or less degree, and will 

 speedily be found so even by those who 

 at first had every reason to be satisfied 

 with its effects. I have repeatedly tried 

 it myself, under divers modifications, 

 and have never failed, sooner or later, 

 to perceive its injurious effects. Indeed, 

 its injuries are for the most part not long 

 in manifesting themselves. The only case 

 in which it is not evidently injurious is 

 in large houses, where the volume of air 

 is great, and the steam is converted into 

 vapour long before it reaches the plants — 

 for it must ever be borne in mind that 

 steam from close boilers, and water 

 heated in open vessels, are essentially 

 different things. Both are alike liquids, 

 and both aeriform, and there the resem- 

 blance ends. Caloric in a sixfold propor- 

 tion has entered into the composition of 

 steam, in the form of latent heat, which 

 is discharged amongst the plants, when 

 the steam is reconverted into vapour." — 

 Rogers, in Gard. May. 



The same excellent authority farther 

 remarks, that, under certain modifica- 

 tions, steam may be employed by causing 

 it to be discharged into a space between 

 the real and the false bottom of a water- 

 cistern 6 inches deep, and" having not 

 less than 4 superficial feet of surface. The 

 false bottom of this cistern is to be of 

 wire or zinc, pierced with very fine holes, 

 and 2 inches above the real bottom. The 

 cistern is to be filled with water, and the 

 steam introduced into the space between 

 these bottoms, when, by heating the 

 water, it will induce the giving off an 

 abundance of vapour, in a state very 

 beneficial to the plants. It is in this 

 modified way that the admission of steam 

 is recommended by Mr Rogers in the 

 case of his conical boiler. 



Mr Beaton has suggested the applica- 

 tion of steam highly impregnated with 

 tobacco or sulphur, for the destruction 

 of insects ; and we have found the bene- 

 ficial effects of mixing sulphur, and also 

 the unrolled leaves of tobacco, in evapo- 

 rating pans, placed on the top of the 

 pipes — as well as the fertilising effects of 

 guano, pigeon-dung, and urine, used in 

 the same way. The ammoniacal fumes 

 given out by the use of these latter bring 

 the atmosphere of a hothouse or pit to 

 about the same state as did the old- 

 fashioned dung-beds, known, notwith- 

 standing their dirty appearance, and 

 great waste both of labour and manure, 

 to be so pre-eminently valuable for the 

 restoration of sickly plants, the vigorous 

 growth of healthy ones, and the total 

 destruction of insects. 



We have already stated that earthen- 

 ware boilers and pipes have been recom- 

 mended ; and indeed there are instances 

 of their being in use, and fully answering 

 the expectations of those who have re- 

 commended them. We have also, in 

 another part of this work, spoken of the 

 cements used for joining metallic boilers 

 and pipes. The following is used in 

 forming connections between earthenware 

 boilers and pipes of the same material : — 

 red or white lead, painting over the parts 

 to be brought together two or three times 

 with oil, so that the parts to be joined 

 may be well saturated. Cotton wool has 

 been recommended to be mixed with the 

 lead, which has the effect of preventing it 

 from cracking. This latter preparation 



