Section III., 1913. [151] Trans. R.SX'. 



Records of Differences of Temperature between Mount Royal and McGill 

 College Observatory , Montreal. 



By Professors C. H. McLeod and H. T. Barnes. 



Fifth Communication. 



(Read May 28, 1913) 



In four previous communications we have had the honour to submit 

 the results of the series of records which we have been making of the 

 differences of temperature between the summit of Mount Royal and 

 McGill College Observatory. These records have shown two important 

 facts, i.e.: 



(1) The variations of the difference curve give valuable indications 

 of the approach of temperature changes at Montreal. 



(2) A study of the average differences for each month shows that* 

 some important relation exists between the average monthly tempera- 

 ture difference between the two levels, and the deviation of the tempera- 

 ture at the lower level from the average of the previous 38 years. 



Unfortunately during the year 1908 the Mountain cable became 

 defective at several points, and after a heavy thunder storm was practi- 

 cally destroyed. The observations were perforce discontinued until 

 such time as a new cable could be procured. 



Thermographs were established on Mount Royal and comparisons 

 made of the records at the high level with those at the lower level. 

 Our attempt to maintain the continuity of the observations, which was 

 so important, was not successful owing to the difficulty of making 

 the self-recording thermographs accurate enough. For two summers 

 a station was maintained on the summit and at the base of Abbotsford 

 mountain, where Dr. Barnes gave personal attention to the records, 

 For this purpose two self-recording thermographs were used. While 

 the general results of our thermograph comparisons were entirely in 

 accord with our previous results, it was again found impossible to ensure 

 sufficient accuracy in the instrument for the object in view. In our 

 opinion no comparison of records taken by separate instruments can 

 yield the information which is readily obtained on a single recorder 

 giving the differences on one sheet. 



Present Equipment. 



During the Summer of 1912 a new cable was installed through the 

 kindness of Mr. R. F. Stupart, Director of the Meteorological Service. 



