Page:The character and extent of air pollution in Leeds - (A lecture delivered before the Leeds Philosophical Society, on March 3rd, 1896.) By Julius B. Cohen (IA b21534160).pdf/14

This page has been proofread, but needs to be validated.

14

magpie, shot near Stainbeck Lane, who bears evident signs of his town residence. Not only are the white feathers badly discoloured, but there is a striking absence of the gloss and beautiful iridescence of the black ones, visible in this country magpie.

Finally, I must mention another effect of smoke, and that is the amount of light absorbed by the smoke-cloud hanging over the city. We are not blessed with too much light at any time, especially during the winter months, and yet the smoke in some parts of the city absorbs about one-quarter of the total daylight. I have registered by a well-known method^[1] the total daylight on a spot on Woodhouse Moor (a high open park lying to the north-west of the town), nearly every day during the past four months. Messrs. Wood and Bedford, of Kirkstall Road,^[2] very kindly permitted their chemist to do the same, and to him I desire to acknowledge my indebtedness. A similar set of experiments have been carried out here on the roof of the Philosophical Hall.

LIGHT TESTS.

Being a comparison of the total daylight in different parts of Leeds.
Date—1895.	Woodhouse Moor.	Philosophical Hall.	Kirkstall Road.
July 1— 7	not recorded	78·30	——
8—14	„	88·30	83·60
15—21	„	61·70	60·60
22—28	„	65·30	58·50
Nov.10—16	22·94	not recorded	20·61
17—23	15·92	„	12·25
24—30	10·20	„	6·10
Dec. 1—7	10·90	„	10·34
8—14	18·30	„	7·17
15—21	4·50	4·80^{[T 1]}	3·53
29— 4	2·60	1·99	1·53
Jan. 5—11	4·65	2·32	2·51
12—18	7·88	5·60	5·51
19—25	8·17	5·90	5·47
26— 1	13·66	9·02	8·04
Feb. 2— 8	6·56	7·20^{[T 1]}	7·58	^{[T 1]}
9—15	8·28	9·05^{[T 1]}	10·57	^{[T 1]}
16—22	3·82	4·40^{[T 1]}	3·26
To economise space the results for each week are added together. ↑ ^1.0 ^1.1 ^1.2 ^1.3 ^1.4 ^1.5 The six numbers marked with an asterisk are exceptions to the general rule. For some unexplained reason, the amount of light registered on these dates is greater in the smokier parts of the town than on the open moor.

↑ The method used was to estimate the amount of iodine liberated on exposure from a mixture of potassium iodide and sulphuric acid. The numbers represent cubic centimeters of thiosulphate solution used.
↑ The position of these works would be a little to left of the centre of the view, shown in the frontispiece.

[T-3] 1.0 ^1.1 ^1.2 ^1.3 ^1.4 ^1.5 The six numbers marked with an asterisk are exceptions to the general rule. For some unexplained reason, the amount of light registered on these dates is greater in the smokier parts of the town than on the open moor.

[1] The method used was to estimate the amount of iodine liberated on exposure from a mixture of potassium iodide and sulphuric acid. The numbers represent cubic centimeters of thiosulphate solution used.

[2] The position of these works would be a little to left of the centre of the view, shown in the frontispiece.

[1]

[2]

[T 1]