474 



REPORT 1891. 



carried on at Cowm and Spring Mill Reservoirs, permission to do this 

 having been obtained from Mr. W. Tomlinson, the manager of the 

 Rochdale Corporation Waterworks. 



The observations began on January 1, 1890, and a synopsis of the 

 results obtained is given below. A record of the rainfall and the number 

 of days on which rain fell has also been included. The hour for observ- 

 ing the instruments is nine o'clock in the morning, but at Cowm during 

 the month of Januaiy 1890 the readings were taken at twelve o'clock, 

 noon, and in consequence a considerable difference will be remarked 

 in the mean temperatare of the atmosphere at the two stations in that 

 month. 



Both reservoirs lie in valleys running nearly north and south (open 

 to the south) about one and a half mile apart, and from three to four 

 miles north of Rochdale. Cowm, the larger reservoir of the two, is 816 

 feet above sea level, and its di-ainage area is 900 to 1,000 acres. Spring 

 Mill is 771 feet above sea level, and has a drainage area of 500 to 600 

 acres. 



The accompanying table sufficiently explains itself. The figures at 

 both stations differ but little, but in column iv. it will be noticed that 

 the monthly range of ivater temperature has been generally greater at 

 Cowm than at Spring Mill ; the extreme oscillation during six months 

 covers 25°'5 at the former and 25°'2 at the latter station. The wide 

 difference in the fluctuations of air and water temperatures is brought 

 out more strikingly in the chart. 



Curve I. — Cowm Reservoir, Rochdale. 9 a.m. 

 Ai r M/nt-^ 



On three occasions in the months of June and July the temperature 

 of the principal feeding stream to Spring Mill Reservoir was taken, and 

 it was found to be 5°"7, 5°'8, and 5°'3 respectively colder than the main 

 body of the water as tested near the overflow. The first of these obser- 

 vations was taken at 9 o'clock in the evening, and the other two at the 

 usual observing hour. 



Mr. James Diggle, C.E., F.G.S., has also thermometric observations 



