November 25, 1S69. ] 



JOURNAL OF HORTICULTURE AND COTTAGE GARDENER. 



•Ul 



THE PROPER SETTING OF A SADDLE BOILER. 



HEPlE has teen so much said lately on the 

 dili'erent forms of boilers and methods of 

 heating, nearly every maker of boilers having 

 invented or patented new forms— each of 

 which, if we believe the advertisements, is 

 superior to any other, and more economical 

 in point of fuel — that I feel it is rather bold 

 of me to venture to add anything upon so 

 well-worn a subject. It seems to me, how- 

 ever, that nearly every boiler-maker, in en- 

 deavouring to outvie his rivals in the trade in the invention 

 of new forms, is making the foi'ms so complex as to add 

 materially to the difficulty of keeping boilers in working 

 order, and from the inequality of expansion and con- 

 traction, adding a great element of weakness. In endea- 

 vouring, too, to make all the use they can of the vertical 

 action of heat, they are forgetting one of the primary laws 

 of the radiation of heat — " That heat radiates equally in 

 every direction ;" or, I might express it in another way, 

 that the secondary law of heat, " That heated air and the 

 products of combustion rise," seems to swallow up the 

 Ihst or more important law, that heat radiates equally in 

 every direction in right lines, and varies in intensity 

 according to the square of the distance from the source 

 of heat. I speak of this as the primary and most im- 

 portant law, because it is owing to this law of the pro- 

 pagation of heat thi'ough a transparent medium like the 

 atmosphere that we are indebted for the heat of the sun. 

 Tliis transmission of heat through transparent media oc- 

 curs with the same velocity as light itself 



Why I am inclined to think that this, the primary law 

 of heat, is much neglected, or rather set aside, is that, 

 in talking over the matter with many gardeners, I have 

 found nearly every one thinks that the heated products 

 of combustion bi'ought over the top of a boiler only heat 

 the brickwork above, and are of little benefit to the boiler 

 itself Now I maintain, on the contrary, if an ordinary 

 saddle boiler is properly set with brickwork •'* inches from 

 the side, and arched over the top, so that the heat from the 

 tire shall traverse all round and over the top of the boiler, 

 in the same way as ovens in the present close kitchen 

 ranges are heated, that the heat given off to the boiler by 

 the flufe is greater than the heat from the fire on the inner 

 surface. I will take first the case of an ordinary saddle 

 boiler, we will say 2 feet long, ■J.-i inches wide exterior 

 measure, and v!o inches high — to take a rough measure in 

 square inches, the interior surface will be about iloO square 

 inches, the exterior about 1250 square mches, the wliole 

 of wliich exterior surface may be heated from the flue. 

 Taking into consideration that every time the tire is 

 mended, the coal, tiU it is thoroughly igiiited, gives no 

 heat near tho furnace door, and that owing to the laws 

 of heat the drauglit from the chimney carries the heat 

 away directly to tho farther end of the boiler, it will be 

 seen that only ono-half of the interior of the boiler re- 

 ceives the full benefit of the fire, while the whole of the 

 exterior of the boiler is heated ; and it seems to me ab=urd 



Ko. 45;.— Vol. XVII., New Series. 



to say that this contracted body of heated air in rapid 

 motion should be hotter on one side than the other — ;. e., 

 that it should heat the brickwork above, hut not heat the , 

 boiler below. 



Another objection which has been raised is, that this 

 heat applied to the top of the boiler does no good, because 

 as heated water rises the water at the top is hotter than. 

 the water at the bottom of the boiler, and tliat we ought 

 to heat the water where it is coldest. This. I need hardly 

 say, is entirely aa imaginary disadvantage. The whole of 

 the proper working of heated water depends upon the, 

 circulation of water in the pipes, fi-om the law of heated- 

 water being lighter than cold water, and the superheating 

 helps to increase tliis circulation. It may not be generally 

 known that the rate of expansion of water increases very 

 materially as it approaches boiling-point : thus, betweea 

 ('i8° and 176°, the volume of water increases ,;;;„ ; betweett 

 170° and 21^" it increases ,lf;o : or in other words, lono parts, 

 of water at 212 become lisc, at 17(;'' Fah., and 960 at, 

 (;s° Fah. It is very true, again, that in a large, long hori-, 

 zontal flue the upper part is hotter than the bottom, but 

 in this case the products of combustion are always seeking 

 to rise, and the hottest and lightest air beats against the 

 surface of the flue ; but what is an argument ui a long ; 

 horizontal flue, is no argument in the confined and con- 

 tracted flue round a saddle boiler. iVny mason, too, who- 

 is familiar with setting sheet-iron ovens, knows that an 

 oven is as much heated from the top as it is from the 

 bottom. 



There are several modifications of the old saddle boiler, 

 which, no doubt, when properly set are superior to it ; 

 but, then, at the same time, they are more expensive. 

 The terminal saddle and Ormson's concentric are both 

 useful modifications. About two months ago (September 

 Kith), I was over at Jlr. Pearson's, of Chilwell, and saw 

 Foster's boiler, which is also an improvement on the old 

 saddle, and seemed to be doing its work well, tliough there- 

 was a large " hatful " of coals on when I saw it, or at all 

 events the man whose head would suit the hat ought tO' 

 have a good deal of brains ; and with due deference to 

 Mr. Pearson, I do not think he has done the boiler justice 

 with the way he has set it, and except that he utilises the 

 heat in his flue by making it pass through the whole 

 length of a double span vinery, I should have said that 

 much heat from the fire is wasted, and a great deal of 

 heat from the boiler itself goes to heat the brickwork in 

 which it is set. I also do not like the exterior elbows 

 and pipes which connect the diiferent parts of the boiler 

 together, still I think it is one of the best modifications of 

 the saddle I have seen. 



From boilers I am naturally led to the position of pipes, 

 and also to the position of boilers in regard to the pipes. 

 A very great mistake I often see is that the pipes in many 

 vineries are laid on the ground, or so near the ground that 

 nearly half of the heat from radiation i.s lost, and only 

 goes to warm the surface of the adjoining ground. Pipes- 

 ought to be placed with as free a circulation of air round 

 them as possible, aid in plant houses there is Jio better 

 pace than under the .stagi's. allowing fbn air from the 



X.>. IIOI.-VCL, XLII., S^f-IES, 



