OF ARTS AND SCIENCES. 45 



This was the first set of observations made after a rather impor- 

 tant change in the ajiparatus, and shows lack of skill. The next 

 series, made the same day, is somewhat better. The same thermopile 

 was used, but contact was during the latter part of compression, 

 just before admission of new steam, near the point K in Figure 5. 



While such observations as those just recorded were being made, 

 one observer was usually engaged in taking indicator diagrams from 



