224 
Proceedings of the Royal Society of Edinburgh. [Sess. 
very pure air, was again selected. Before going there, however, the 
method of testing by means of the expander was systematised and 
developed, so as to make it give more definite information than had been 
previously got from it. Further, the method of illuminating the test- 
flask had to be changed ; in place of gaslight, sky light had to be used. 
It was therefore necessary to practise here with the new arrangements 
before going north, so that the readings at the two places might be taken 
under the same conditions. Tests were also made on my return home, with 
the same arrangement as to lighting. These were made in the end of 
September and beginning of October last. 
Table II. — Nuclei in the Air. 
Date. 
Hour. 
Number of 
Showers to 
clear at 
Number of 
Showers to clear 
at Higher 
Expansions. 
umber of 
;t Particles 
the Air. 
Wind. 
1 Remarks. 
8 p.c. 
2 p.c. 
4 p.c. 
G p.c. 
8 p.c. 
Sept. 
22 
11 
6 
4 
2 
1 
S.W. -5 
Falkirk air. 
23 
11.30 
6 
5 
2 
i 
£ 
... 
... 
S.W. 1 
5 5 
27 
12 
1 
8 
5 
3 
2 
... 
E.N.E. 1 
Loch Awe. 
55 
3.30 
1 
8 
7 
4 
2 
6,000 
5 5 
Local pollution. 
55 
4.30 
0 
4 
2 
2 
1,100 
Free from local pollution. 
28 
3 
2 
3 
3 
2 
10,000 
E. 
Local pollution. 
29 
11.30 
4 
8 
9 
3 
1 
14,000 
E.N.E. 2 
55 
55 
12 
1 
2 
1 
1 
1,250 
Free from local pollution. 
5 ) 
3 
2 
5 
6 
2 
10,000 
55 
Local pollution. 
55 
3.30 
0 
4 
2 
i 
4 
1,125 
55 
Free from local pollution. 
30 
10.30 
3 
5 
6 
1 
14,000 
55 
Local pollution. 
55 
11 
0 
2 
1 
1 
4 
500 
55 
Free from local pollution. 
55 
3.40 
3 
3 
3 
3,500 
Air in room. 
55 
3.45 
16 
4 
2 
... 
... 
Air in room after burn- 
Oct. 
1 
11.45 
2 
2 
1 
2,500 
S.W. *2 
ing wax vesta. 
Free from local pollution. 
5 5 
... 
2 
3 
2 
2,500 
... 
Air in room. 
5 ) 
. . . 
14 
4 
2 
. . . 
After burning wood 
4 
12 
4 
3 
1 
20,000 
Calm 
match. 
Falkirk air. 
55 
4 
6 
4 
3 
25,000 
55 
55 
5 
1 
5 
2 
2 
1 
4 
7,000 
W.S.W. 2 
55 
55 
4 
4 
2 
1 
7,400 
IV. 
55 
6 
11 
3 
3 
1 
6,000 
W.S.W. 1 
55 
55 
4 
6 
4 
2 
22,000 
55 
„ 
; 
The method of making these tests will be understood from an examina- 
tion of Table II. In the first two columns are entered the date and hour of 
the observation. Then after the test-flask has been filled with the air 
to be tested, and its inside walls wetted, the two stopcocks are closed, 
the expander stop having been previously set at 0. The stop is now 
moved back to give an 8 per cent, expansion, and the handle Z slowly 
