6 
attains any particular advantage from having its amount 
of lime salts lower than some 10 or so grains per gallon, 
though doubtless it is better that this should be very small, 
than that it should be excessive. To give a fuller indica- 
tion of the quality of the water of Thirlmere, we have taken 
the liberty of appending to our results, those obtained by 
Dr. Roscoe from a sample of the same taken in February 
of this year. Now it will be seen that there is a certain 
difference between the results of these samples, more espe- 
cially with regard to our “lower” one. On examination, 
however, the difference will be seen to be one of “ degree” 
only, and not of “kind,” and entirely confined to the 
mineral, and in this case the least important items. It is 
explained by the fact that the rain-fall some little while 
before the taking of the respective samples had been very 
different, the longest period of dryness perhaps which we 
have had this year having occurred just before the taking 
of those of the present paper. We should therefore expect 
that the solid matters would be higher, and find them to be 
so by about one and a half grains per gallon, the total in 
either case being insignificant. It would perhaps not be 
wide of the mark if we said that the analyses of Dr. Roscoe 
and ourselves show the water at its best and its worst as 
regards ordinary variation. This variation it will be seen 
is not greater than may occur at the same time in different 
parts of the lake, as shown by our upper and lower samples, 
these analyses also indicating a slight gradual increase of 
dissolved material as we approach the foot of the lake, 
where the solvent action of the water upon its bed will 
have accumulated and the fresh water received from the 
tributaries is lowest in amount. This gradation of quality 
will, of course, only be true of the lake under its present 
natural conditions. 
The variation of the organic constituents of the water at 
the different dates is not so marked. From the behaviour 
of the solid matter during ignition we should say that the 
carbonaceous matter, of which there is a perceptible amount, 
is almost entirely of a vegetable nature. 
