Section III., 1904 [ 71 ] Trans R. S. C. 



XII. — Notes on the Difference of Temperature, McGitl College Grounds 

 and Mount Boyal, Montreal, Canada. 



By Peof. C. H. McLeod and Dr. Howard T. Barxes. 



(Read June 23, 1904.) 



In 1897 the British Association made a grant of £50 towards the 

 investigation of the changes in temperature due to differences in alti- 

 tude at Montreal. In the early dimmer of 1S99 the Callonder electric 

 recorder was installed at McGill College, one thermometer being on the 

 summit of Mount Royal and the other on the grounds of the College. 

 The conducting leads were jSTo. 14 copper with ordinary composition 

 insulation. ,Tihe records obtained in dry Aveather were satisfactory 

 but the insulation was not sufficient for wet weather conditions and 

 the work was abandoned until such time as a lead-covered cable could 

 be procured. 



A gift of $300 from Sir AVm. Maedonald placed, tlie funds for 

 ,1ihe erection of the cable at our disposal in the summer of 1903, and 

 tihe records were obtained under the improved conditions as to wire 

 connection, in July of that year. 



The mountain thermometer is 47 ft. above the ground and 800 

 ft. above sea level and is enclosed in a single screen cage. The ther- 

 mometer on the College grounds is 4 ft. above the surface of the soil 

 and 180 ft. above sea level. It is protected by a double screen. iThe 

 difference in elevation of the two thermometers is as above, 620 ft. Tbe 

 mountain station lies in a direction approximately NW. from that on 

 the College grounds and at a ^horizontal distance from it of about 3,300 

 ft. The length cf the connecting leads is 4,100 ft. Tlhey are of 

 '^'o. 16 copper wire, paper-covered and enclosed in a lead cable which 

 is suspended froon a steel cable on poles. 



A complete set of the differential recorder shoets (reduced to stome- 

 ;what less than one-third the actual size) for the month of February, 

 1904, accompanies this memorandum; also a set of sheets, giving the 

 'temperature at the lower station and the temperature deduced for the 

 higher station by plotting from the diffenence curves. In the latter the 

 tfuU line represents the temperatures at the lower station and the parti- 

 ally dotted line those at the upper station. The* vertical scales as num- 

 bered represent degrees Fahrenheit. 



An inspection of these curves Anil show that any marked change 

 in temperature at the lower station has been heralded by a change 



