MR. G. V. VERNON ON SOLAR RADIATION. 139 



radiation thermometer at Greenwich in the early part of 

 the year. 



From the beginning of i860 to the end of 1864 the ob- 

 servations at Greenwich were made with a black-bulb 

 thermometer in vacuo, and it is satisfactory to find that 

 the course of the annual means is in tolerably fair agree- 

 ment with that of the results obtained at Oxford with the 

 ordinary black-bulb thermometer. 



VI. Solar ^radiation Observations, made at Old Trafford, 

 Manchester. By G. V. Vernon, F.R.A.S., F.M.S. 



Eead November 26th, 1867. 



Mr. Joseph Baxendell, F.R.A.S., having, at a recent 

 meeting of the Physical Section, read a paper on this 

 subject, showing some peculiarities of the distribution of 

 solar radiation throughout the year, I have at his sugges- 

 tion reduced and tabulated my observations bearing upon 

 this point down to the end of 1866, making eleven years 

 in all. Unfortunately the month of August is deficient 

 in six years out of the eleven. The observations were 

 made with Negretti and Zambra^s patent maximum ther- 

 mometers, neither thermometer having any index error, 

 but reading correctly with the standard throughout the 

 scale. 



Taking the difierences between the mean maximum 

 black-bulb reading in the sun, and the mean maximum 

 reading in the shade for each month, we find a minimum 

 in December and a maximum in July. The maximum 

 occurs in the warmest month, but the minimum appears 

 to occur some time before the coldest month arrives, 

 viz. January. If we take the diff'erences between one 



