84 TRANSACTIONS—PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
along the river and its tributaries examples might be cited of the 
same kind of thing, in some cases the sewage being partly purified, 
and in other cases run in in its crude state as at Aberfeldy. Reports 
<yot from gentlemen in several districts we do not feel at liberty to 
make public, and the grosser forms of pollution are being found out 
and stopped by the vigilance of our Medical Officers and Sanitary 
Inspectors; but I have said enough, I think, to bring home the fact 
that sewage—in some cases at least, crude and undiluted sevage, 
enters the Tay, and we shall ask a little later, are the natural and arti¬ 
ficial means at our disposal sufficient to effectually purify our water 
supply from the contaminations which undoubtedly it contains. 
Let us now examine the results of the two sets of analyses of the 
River Tay, and from these we shall get a general impression of the 
kind of water we have to deal with. The first set of samples were 
drawn from the river at the different points mentioned on January 
-ISt, when the river was in spate and slightly muddy. In each case 
we filtered off the suspended impurities, and then determined the 
dissolved impurities, dividing them into volatile substances, or those 
driven off by heat, which are chiefly organic matters and ammonia 
salts, and saline substances or those not driven off by^ heat. 
These two added together give us the total solids dissolved in the 
water. We also determined the chlorine, the hardness, and the 
temperature both of the water when drawn from the river and of 
the air at the same time. 
TABLE I. - ANALYSES OF TAY WATER, DRAWN JAN. 31st, 1893. 
(river in SPATE.) 
Solids in suspension, 
,, c ( Volatile, 
„ c-B) Saline, 
I. 
II. 
HI. 
IV. 
V. 
VII. 
VIII. 
<1; 
> 
0 
£ 
U 
*3 
oJ 
*> 
% 
Q 
*■ 7 : 
a 
G 
rt 
U 
• V 
7 > 
rth Water 
Supply. 
< 
V 
< 
b/D 
0 
hJ 
< 
< 
< S 
<V 
W 0 
•6 
17 
4-6 
2 '4 
I ’6 
— 
I ‘2 
2 
•8 
2‘6 
2'0 
2-4 
3-2 
2'8 
3-0 
I 
•3 
1 'O 
I ‘O 
I ‘2 
14 
2-4 
I ‘4 
IX. 
• u 
rt D 
I ‘6 
27 
1*8 
,, S ( Total, 
- 
4-1 
3-6 
3'0 
3-6 
4-6 
5’2 
4’4 
4’5 
Chlorine, 
- 
'60 
•60 
•53 
•60 
’55 
•90 
•60 
•60 
Hardness, Temporary, 
,, Permanent, 
•5 
2‘0 
•5 
2'0 
•2 
2‘2 
• ^ 
d) 
2-3 
:> 
2 *2 
•4 
3 ’o 
■5 
2’5 
■4 
2-4 
Total, 
- 
2-5 
2-5 
2-4 
2’6 
27 
3’4 
3-0 
2-8 
Temperature of Air 
Water 
i * 
' 4 
7 
6 
6 
5 
10 
6 
5 
2 
9 
5 
8 
5 
9 
7 
Time of Day, - 
- 
10 
a.m. 
5-30 
p.m. 
5-15 
p.m. 
1.30 
p.m. 
II.15 
a.m. 
3-43 
p. m. 
9-45 
a.m. 
3.20 
p.m. 
