90 MR. JOSEPH JOHN MURPHY ON AN 



instantaneity of action under very ordinary thermal 

 changes in the radiance from the sky. The influence of 

 the sun's rays at daybreak is almost always shown^ for 

 some minutes at any rate, before the sun is seen, and 

 occasionally, it would seem, even for hours before his time 

 to rise. 



It is not, however, now my purpose to dwell upon the 

 interesting changes which take place in the intensity of 

 the thermal radiance from the sky, my present object 

 being to describe an instrument by means of which they 

 may be recorded or observed. Doubtless in several of its 

 details the " radiograph " may be improved, notably in 

 the condition of its bulbs, and it would unquestionably be 

 better if it computed for itself the areas included by its 

 curves. This, I dare say, I shall presently enable it to do. 

 Meanwhile, as a recorder of the duration and intensity of 

 radiant heat, the instrument, so far as I have seen, is the 

 only one whose readings are uninfluenced by the tempera- 

 ture or the pressure of the air. 



XIII. On an Extension of the ordinary Logic, connecting 

 it with the Logic of Relatives. By Joseph John 

 Murphy, F.G.S. Communicated by the Hev. Robert 

 Harley, F.E.S. 



Kead October 7th, 1879. 



The present paper has been suggested by the section on 

 Elementary Relatives in Prof. Pierce's " Description of a 



