Section III., 1906. [ 141 ] Trans. R. S. C. 



IX. — Further Notes on the Difference in Temperature hettueen McGill 

 College Grounds and Mount Royal, Montreal. 



By Prof. C. H. McLeod and Dr. H. T. Barnes. 

 Part I. — Presented Mat, 1905. 



Since the presentation of our preliminary report to the EoyaJ 

 Society of Canada last year on the differential temperature records 

 between the summit of Jlount Koyal and the McGill College Observa- 

 tory* another set of records has been obtained during the winter 

 months, which help to confirm our (conclusions in regard to the value of 

 these records as a means of foretelling temperature conditions. Unfor- 

 tunately we cannot at the present time make our second communication 

 as; complete as we shoula like, owing to a serious fault which developed 

 in our long distance cable shortly after the end of May, 1904. This re- 

 sulted from the giving out of the insulation in the cable as the warm 

 weather set in, the degree of insulation being so impaired as to make 

 temperature records impossible. 



After a long search involving considerable delay, the fault was 

 located in a cut which had been made about a year previously by some 

 malicious person. The repairs to the cable at this point had not been 

 sufhcientiy carefully made by those in charge of the work, and water had 

 percolated through a portion of the junction of the lead sleeve placed 

 over the splice. During the cold weather any water which had entered 

 produced no appreciable error, but with the advent of the warm weather, 

 and the spring rains matters grew steadily worse. 



Owing to the stress of other duties which prevented adequate time 

 being devoted to the work it was late in the autumn of 1904 before the 

 cable was sufhcientiy repaired to make further readings possible. The 

 repairs consisted in opening the cable at the splice, drying it out and 

 adding a new lead sleeve. 



Tests of insulation then followed which showed that the separate 

 wires were in fair condition but not perfect, amounting to two or three 

 megohms for the worst cases. As the cold weather was approaching, 

 when any fault of insulation would be reduced to a minimum, it was 

 decided to go on with the work and defer until spring any further 

 repairs to the line. 



The determination of the absolute temperature of the mountain top 

 compared with that of the observatory depends on so many factors that 



' Elevations above sea level respectively 754 and 180 ft. 



