220 I >r. A. A. li'.mil'iuit. du 



All the instruments wore very carefully standardised by means of 

 observations extending over three days, in October, 1898, and on 

 October 6, 1899, taking advantage of a visit from Mr. Griffiths, I had 

 the 6-in. thermometer dug up, and we examined its zero point after 

 exactly a year's continuous observations. The readings agreed to within 

 0-004 C., being 



In 1898 0-306 



In 1899 0-302 



For reasons given in the paper, it was not thought necessary to 

 re-examine the boiling point. For another thermometer (A), kept in 

 the observing room, the fundamental interval was found to have 

 remained practically unchanged, being 



In 1898 101-067 



And in 1899.. 101-059 



II. Discussion of the Observations. 



The first step in the discussion of the observations is to group them 

 into monthly means, and thence to deduce the harmonic expressions 

 which will represent the readings of each thermometer throughout the 

 year.* These monthly means expressed in degrees Fahrenheit are 

 given in the following table : 



Mean Monthly Temperature of the Ground at the Radcliffe 

 Observatory, Oxford, 1899. 



* Professor W. Thomson, " On the Reduction of Observations of Underground 

 Temperature," ' Trans. Roy. Soc. Edin.,' vol. 22, p. 409. 



