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J. THOS. PATTERSON. 



partition in which are two openings, m and n. The regulator 

 bulb passes through the former of these holes. In the first apart- 

 ment the water is heated by the incandescent atX; in the second 

 is the egg-cell ; and the third is the passage for the water from 

 B to A. The arrows indicate the direction of the main current 

 of water, and the principle by which this current is maintained is 

 simple. Thus the water on being heated at X spreads out over 

 the top of apartment A and enters B through opening m, and 

 consequently flows past the thermoregulator bulb and around 

 the egg-cell. Apartment C, in addition to being that portion of 



Fig. 2. 



the incubator situated farthest from the source of heat, is so con- 

 structed that a considerable portion of its surface is exposed for 

 radiation, and hence, the water in this chamber is gradually cool- 

 ing, and in so doing will flow back through n into A. It should 

 be added that the lower layer of water in A is also heated by 

 the incandescent, at least sufficiently to raise it to a higher tem- 

 perature than that in the lower part of C, and consequently the 

 water in this latter region passes into A. At the same time the 

 upper layers of C in turn cool and sink. There is maintained 

 throughout the three apartments, therefore, a constant current, 



