14S 



PRorET?ni\(i>^ OK rill.; 



considers that there ean he on the wliole no douht that three 

 inch or four iiuli pipes are exeeedin^ly preferable to smaller 

 ones, where eeononiy of fuel and uniform adjustment of the teni- 

 jK'rature for several hours, are the primary ohjeets. 



In determinini:; the proportion that should be borne by the sur- 

 faee of pipe to tiie surface of ^lass, the author referred in terms 

 of j^reat praise to iMr. ("harles Hood's most valuable treatise on 

 hot water a|)paratus. I'onnerly, he observed, the most prepos- 

 terous blunders were eounuitted on this ])oint, — almost all the 

 earlier a|)|)aratus were incomj)etent to the work re(]uired of them, 

 the (pjantity of l)i|)e beinj;- insullicient to ])r()du(e the beat de- 

 sired, while the boiler beini;- lar^e and of very defective construc- 

 tion, a vast (piantity of fuel was burnt to waste ; the gardener 

 lindinj^ his heat deficient, naturally stoked up his fire and threw 

 on fuel in the hope of increasing it, but the only result of his 

 labour was the more rapid destruction of the boiler itself, liut 

 the publication of Mr. Hood's work caused the principle of cir- 

 culation in hot water ai)paratus, to be better understood. If how- 

 ever the earlier aj)paratns were njostlv deficient in the quantity 

 of ])ipe enii)loyed, many of those more recently erected err in the 

 opi)()site extreme. The errf)r arising- not from any defect in the 

 data or in the calculations, but from assuming, as the minimum 

 of external air, a temperature which very rarely occurs in this 

 country, and which lasts for so very short a time that no build- 

 ing has time to cool down to a corresponding temperature ; a 

 power of 30° for green-houses and of 4.5° for hot- houses, is in 

 Mr. Rogers's opinion ample under any circumstances. It may 

 be urged that it is always easy to work an Jipparatus below its 

 power, and that such an arrangement is economical of fuel, 

 which within certain limits is true j but if the quantity of pipe 

 materially exceeds what is necessary, the only means of keeping 

 the house at a moderate temperature is by leaving the furnace 

 door open, and a great waste, instead of any economy of fuel, 

 necessarily results. 



The author then proceeded to consider the expediency of heat- 

 ing several houses from the same boiler. To this arrangement 

 he saw no objection, provided the same number or extent of 

 houses are always to be heated at the same time ; but serious 

 inconvenience will be found to arise from an attempt to heat 

 with the same boiler two buildings, in one of which occasional, 

 and in the other permanent heat is required, and this inconve- 

 nience will be great in proportion to the size of the buildings, 

 especially, if as is generally the case, the hothouse is small, and 

 the greenhouses or pits more extensive. The same inconvenience 

 will also be felt if two vineries, one to be forced at a later period 

 than the other, be heated from one boiler. 



The only scientific method of obtaining a different temperature 

 in stoves heated from the same boiler, is by allotting to each 



