VARIOUS INCUBATORS. 69 



of glass, B, on the top, the lever of the regulator A raising 

 or lowering a valve over the centre. The lamp, j, is fur- 

 nished with a wire gauge, K, to which the top of the flame 

 is set. The heated air rises through the central aperture, 

 1 1, in a water tray constructed in two stories, the lower one, 

 H H, being filled with water, which rises by capillarity 

 through the cloth, L, into the higher inside trough, GG-. 

 Thence the moist vapour, as well as heated air, passes into 

 the incubator through the central square aperture, also 

 lettered I, surrounded by the perforated guard or shaft, D ; 

 E E and F F are the bottom of the hatching chamber, formed 

 of a flexible covering which " sags " between rods, and which 

 being drawn along or pushed back by the rods, F F, gently 

 and steadily, turns all the eggs at one time. An arrange- 

 ment like this is applied to some other incubators. 



We figure the regulator separately in Fig. 20, being 

 peculiar in both form and action. It is a metal reservoir 

 rather than capsule, resembling a shallow funnel with closed 

 top and bottom, and containing a portion of volatile fluid 

 properly adj usted for temperature. The peculiarity is, that 

 while the tubular portion descends into the egg-chamber, 

 the broader top face is exposed to the outer air. This prin- 

 ciple we have not happened to come across as yet in any 

 other machine, and it seems to us valuable, since it antici- 

 pates external changes in the temperature, which have to 

 be considered in an incubator, as described further on. The 

 precise working of the valve as the top of the funnel bulges 

 with the heat, is of course adjusted as usual by the milled 

 head of the screw. 



Very great objection has been made to this simple class 

 of machines, especially by manufacturers of tank machines, 

 who say that they " cannot " hatch properly ; and a very 

 recent treatise on incubation states that the method of 

 passing heat from the lamp straight into the chamber u .is 



