138 
large section of Manchester, and as these winds blow four- 
fifths of the year, Smedley has the lion’s share of the town’s 
smoke. 
The slips were changed at 8 morning and at 6 evening, so 
that they represent alternately day and night, and I may 
say that the results almost completely ignore the effects of 
large chimneys, the night slips being as decidedly acted 
upon as the day’s, and none of them more so than the night 
between Saturday and Sunday morning. The effects are in 
remarkable connection with the state of the wind or set of 
the atmosphere, so much so that if shewn a slip exposed 
there for 12 hours I could almost tell from it in what direc- 
tion the wind had been. During most of the days and nights 
of exposure the wind was south, coming over the broadest 
section of Manchester ; on Sunday it changed to east, coming 
over Harpurhey and Moston, although the apparent 
smokiness was not much less the colouring was slighter. 
Gilda Brook, near Eccles, where the other slips were 
exposed, is west of Manchester, and fully 3 miles from the 
centre of the town, and there, even with an east wind, the 
* 
diffusion of the gas is seen in the more slight colouring. 
I am still continuing the exposures, and shall, probably, 
in addition to this, attempt to measure the actual quantity 
of S0 2 on some day when Smedley has the benefit of the 
fullest sweep of the Manchester atmosphere. 
As to the effects of these gases upon vegetable life I have 
full proof at Smedley, vegetable life on the whole of that 
side of town is a mere struggle for existence. 
As an instance, as I am leaving it for the opposite side, 
where only a due north wind, which almost never blows, 
will bring me the smoke, I have been able to try its effects 
upon about 20 plants of camilias: these I had at Smedley, most 
of them for eight years, and the blooms had dwindled down 
year by year till, in the Spring of 1868, 1 had only 3 or 4 miser- 
able specimens. Early last May I moved them to the south 
