154 



HEATING AS APPLIED IN HORTICULTURE. 



coil of pipes. One end of the draco was 

 inserted into the milarium near its 

 bottom, and the other near its top, (just 

 as our modern hot- water pipes are placed 

 in relation to the boiler.) The water 

 entering at the lower orifice was dis- 

 charged hot from its upper end, and the 

 entire mass of water in the milarium 

 was heated by this circulation in the 

 draco. Cameron, in his account of the 

 Roman baths, gives a figure of an ancient 

 coil-boiler, no doubt formed by a Roman 

 workman, which probably was the type 

 of Perkins' modern system of heating by 

 very similar means. — Vide p. 157. 



It would tend little towards practical 

 utility to give even a very condensed 

 description of the respective merits of 

 all the systems of hot-water heating. 

 We shall endeavour, however, to explain 

 the principles of such of them as we 

 consider to be of most importance. 



Passing by the arguments that have 

 been adduced in regard to the first 

 inventor of this system of heating, we 

 may state, that whatever knowledge the 

 first three and the fifth of the names 

 mentioned above had of the theory, it is 

 quite certain that none of them brought 

 it into useful operation for heating horti- 

 cultural buildings. 



Mr Atkinson's system was the first that 

 was exemplified in a perfect state. It may 

 be termed the horizontal mode, as the 

 water was made to flow from the boiler a, 

 to the reservoir or turn of the pipes b upon 

 a perfect level, as will be seen by a glance 

 at the accompanying diagram, fig. 162 ; 



Fig. 162. 



and however far most of the others have 

 essentially differed from it in some feature 

 or other, still the principle remains un- 

 changed. 



The construction was as follows : A 

 square or rectangular cast-iron boiler, 

 open at the top, of sizes varying from 3J 

 to about 1 2 cubic feet (according to the 

 heat required) in internal capacity, was 

 placed over a well-constructed furnace, 

 the fire burning under it, and being carried 

 round two or more of its sides in flues 9 



inches wide. To this boiler were attached 

 two cast-iron pipes usually fixed to it by 

 flange joints ; or sometimes by having 

 nozzles or short pieces of pipe cast on the 

 boiler about a foot in length, to which the 

 pipes were attached upon the spigot-and- 

 faucet principle ; the joints being made 

 good with rust, or filings or borings of 

 iron mixed with sal-ammoniac and water, 

 driven as hard as possible into the joints 

 by means of blunt chisels — a collar of hemp 

 or thick millboard being first introduced, 

 to prevent the packing from falling into 

 the pipes. Lead was and still is some- 

 times used, as are also joints of hemp and 

 white lead, and both are useful for tem- 

 porary purposes, as they may be separated 

 again with little trouble. The rust joints 

 are the most secure as well as most last- 

 ing ; for soon after they are formed they 

 become as hard as the iron itself, and 

 quite as difficult to break; indeed the 

 joint of a cast-iron pipe attached in this 

 way is the strongest part of it. 



At the extremity of the space to be 

 heated, according to Atkinson's views, 

 was placed a cistern or reservoir exactly 

 level with the top of the boiler, with a 

 view to equalise the temperature by means 

 of the heated water it contained. The 

 boiler and reservoir were then connected 

 by the pipes. The top of the boiler was 

 covered with a wooden cover 2 inches 

 thick, and fitted into a flange or groove 

 in the top, into which a little water was 

 poured to keep steam from escaping, this 

 simple process being usually termed a 

 water-joint. The reservoir was covered 

 with an iron cover fitted in the same way. 

 The wooden cover was used in the one 

 case to prevent, by its non-conducting 

 properties, the escape of heat ; while the 

 iron cover was used in the other for a 

 diametrically opposite purpose. The 

 boiler was in general set in a niche in the 

 back wall, and within the house, to pre- 

 vent the w T aste of heat. This is the most 

 simple of all modes of heating ; but, as 

 will readily be seen, it is capable of 

 operating only upon a perfect level. The 

 same intelligent gentleman, however, con- 

 structed boilers with closed tops, by means 

 of which he was enabled to carry heat 

 about 30 feet above the boiler. He not 

 unfrequently dispensed with the reservoir, 

 and made the return by an elbow bend at 

 the extreme end of the pipes. If this 



