PROPAGATOR. 



399 PROPAGATOR, SIMPLE. . 



boards thus put in at top and bottom and 

 the tin must be carefully closed with putty 

 and well painted ; the chamber, n, D, sur- 

 rounding the tin will thus form a hot 

 chamber, which will be of material assist- 

 ance in preserving an equable temperatur; 

 should the lamp go out. The lower case 

 being completed, and the tin filled with 

 water, the upper case may be dropped into 

 its place, and all is ready for active opera- 

 tions. 



Through the open front of the lower 

 case a lamp must be introduced, and so 

 placed on a stand or not, according to 

 circumstances, so that the top of the 

 chimney may be about 2 inches below the 

 bottom of the tin that has been utilised as 

 a boiler, and just under its centre. Light 

 the lamp, lay a thermometer on the top of 

 the cocoanut fibre, and watch the mercury : 

 it will soon rise and show that summer 

 heat, or thereabouts, has been attained in 

 the upper case. Steam has been gene- 

 rated in G, and has risen to the under side 

 of the bottom of the upper case, there to be 

 condensed and fall in drops on the slanting j 

 boards round the top of the tin, from which 

 they trickle into the tin itself. The false ; 

 bottom, being a good conductor of heat, | 

 has transmitted the heat derived from the 

 steam generated in the boiler to the air in 

 the box above, and an increase in tempera- 

 ture has consequently followed. This is 

 the whole principle of bottom heating, con- 

 tained, as it were, in a nutshell, and holds 

 good as an illustration of it whatever may 

 be the heating medium. To be complete 

 in itself, the little propagator described 

 should be furnished with a pipe communi- 

 cating with the external air, and rising to 

 a level with the topmost edge of the outer 

 case, by means of which it may be ascer- 

 tained, by the issue of steam or the con- 

 trary, whether or not the boiler is empty, 

 and by which it may be refilled ; but no 

 attempt has been made to explain this 



feature, as the boiler can easily be re- 

 plenished by lifting off the box that covers 

 it in. 



Propagator, Simple. 



Another simple but useful propagator is 

 made in the following manner. A is a case 

 with neither top nor bottom, supported by 

 four wooden legs, B. B. , notched at top as 

 shown, and screwed to ends, which are 

 lower than sides, to allow of the passage 

 over them of two panes of glass, which 



1 



SIMPLE PROPAGATOR. 



work in grooves cut in inner part of sides 

 along the top. Round the bottom are 

 nailed strips to form a ledge, on which rests 

 the boiler D, formed of two plates of tinned 

 iron, the lower one flat and the upper one 

 bent at the edges, and soldered down on 

 the lower plate so as to leave a hollow 

 space between them. Water is poured into 

 this through the funnel E, and at the oppo- 

 site corner, diagonally, is a small pipe F, 

 through which steam finds an exit into the 

 case. The warming is effected by means 

 of a very small lamp, such as is known as 

 a " night-light " lamp. The top of the 

 chimney goes into a hole, in the centre of a 

 saucer-shaped tin, in which it moves freely. 

 Three or four holes are pierced in this tin, 

 which is soldered on to the bottom of the 

 boiler and tends to prevent too great a 

 dispersion of the heated air above the 



