SCIENCE. 
21 
In speaking of quality. Dr. Frankland adheres throughout 
to the strict technical use of the words “impurity” and 
“ pollution,” applying them to all foreign substances present 
in water. This is to be regretted, as they are eminently 
misleading when referring to the quality of water for 
ordinary purposes, and are certain to foster prejudices both 
unfair and mischievous. According to his "use of these 
terms, all mineral waters, iucluding those especially recom- 
mended for dietetic purposes, might be quoted as exceed- 
ingly impure, and loaded with polluting matter. 
The determination of the ammonia is the next point 
considered. It is admitted that the actual quantity of 
ammonia present is, of itself no guide to the purity of water, 
as there are many cases of deep-well water in which the 
quantity is large, though there has been no access of animal 
matter. As, however, ammonia in water is very commonly 
caused by animal matter in a state of incipient decomposi- 
tion, and is found in water polluted by sewerage, in shallow 
well water, and in some cases in river water, the quantity 
present in a given quantity of water is regarded as an 
essential inquiry, and its presence is suggestive of evil. 
Chlorine is present in water chiefly as a constituent of 
common salt, and this is so uniformly found in the liquid 
excrement of animals, that its presence in water is also to 
be distrusted. At the same time, a certain quantity is cer- 
tainly washed out of the air and soil by rain, although the 
proportion of this is not constant. The quantities allowed 
by Dr. Frankland as due to these causes are 0.22 per 
100,000 for rain water, 1.13 for upland surface water, 2.49 
for spring water, and 5.1 1 for deep-well water. The history 
of the water must, therefore, be known before its value can 
be ascertained. It is evident that there are special cases in 
which these quantities are enormously exceeded without 
danger. 
The estimation of nitrogen as nitrates and nitrites is not 
difficult, and may be effected in one of three ways. Each is 
described at some length in Dr. Frankland’s book, and each 
has its own advantages. He prefers that which involves 
the decomposition of the salts into nitric oxide, and the 
measurement of the gas evolved. 
The methods for determining hardness that are suggested 
involve nothing new, and they have been too often de- 
scribed to require notice here. 
The method of determining organic purity by the use of 
permanganate of potash, originally suggested by Professor 
Forchammer in 1850, approved by Dr. Miller and other 
eminent chemists, and brought into use by the late Dr. 
Letheby, has been perfected by Dr. Tidy, and appears to 
produce results so satisfactory, as compared with the com- 
bustion process, when carried on under the most favorable 
conditions, that Dr. Frankland admits its usefulness and 
general accuracy in waters of moderate purity. It is elab- 
borately described by Dr. Tidy in his memoir, and its ad- 
vantages discussed. The prominent objections to the com- 
bustion process, which is still regarded by Dr. Frankland 
as the only secure method of determining the organic ele- 
ments, will also be found fully stated in that memoir. 
It must not be supposed that the analytical determina- 
tion of the foreign substances present in water is sufficient 
to justify a conclusion as to the quality of the water with- 
out a due consideration of all circumstances, not only 
those indicated by the association of the elements, but 
those under which the water has or may have acquired 
them. No chemist, however able and intelligent, is justi- 
fied in giving an opinion as to water submitted for analysis 
without knowing the history of the water, except, of course, 
where there are definite poisons present which enforce an 
absolute condemnation.* Neither the ammonia nor the 
nitrogen, neither the salt nor the hardness, maybe regarded 
alone, without reference to this history. Thus it is that 
while mere analysis is easy, the estimation of waters for 
sanitary purposes must always require very great judgment 
as well as long experience. 
Dr. Frankland gives in an appendix a number of typical 
* It is well that this should be borne in mind by engineers and others 
who occasionally send wa'ers tor analysis with merely a number or other 
private reference. It is not fair to the chemist to require an opinion as 
to the goodness of water, without communicating its source and the cir- 
cumstance under which it has been obtained. Generally the chemist 
should take the sample himself. 
analyses of waters of various kinds and of various qual- 
ities. Adopting a classification suggested originally by 
Dr. Parkes, and modified by Dr. Tidy, he groups all 
waters into two sections — upland surface waters, and 
waters other than upland — and each section he divides into 
four classes — viz., waters of great purity, of medium purity, 
of doubtful purity, and of no purity at all ; determining 
the value in each case by the permanganate process. This 
classification may be useful in some cases, but it is hardly 
of general application, inasmuch as “upland surface 
waters” is a very vague expression. The analyses given 
in this appendix are valuable, and are, we believe, chiefly 
quoted from the celebrated Sixth Report. We venture to 
suggest that they would be less liable to misconstruction 
if the estimate of what in this work Dr. Frankland still 
calls “previous sewerage contamination” were left out. 
This expression is, no doubt, explained (see pages 95-98.) 
as it has often been, and to those who understand the ex- 
planation it really means nothing that in any way affects 
the value of the water ; but when we are told that rain 
water falling in London on November 8, 1873, contained 
1,490 parts in 10,000 of this mysterious essence — that the 
deep-well water from the magnesian limestone contains, on 
an average, nearly ten times as much, and the upland sur- 
face water from the lower London tertiaries none at all, we 
confess to a feeling of wonder that so misleading a title 
should continue to be used in reference to waters 
whose real value for dietetic purposes is not, and cannot 
be, in the smallest degree, influenced by so ugly an ex- 
pression. The term has been withdrawn from the official 
returns describing the state of the London water, and it 
would be well if it could be expunged from the literature 
of analytical chemistry. 
We have already alluded to some of the reasons of Dr. 
Tidy for rejecting Mr. Wanklyn’s “albumenoid ammonia ” 
process, and have pointed out that they are fully recog- 
nized by Dr. Frankland. This method is, however, by much 
the easiest of all for determining the organic constituents 
and for that reason is very widely adopted. It is de- 
scribed in detail in Mr. Wanklyn’s volume already re- 
ferred to, and one of the means of determination involves 
the precise comparison of shades of color. A possibility 
of personal error is thus introduced, which detracts very 
seriously from the value of a method which appears in 
other respects to be doubtful in its conclusions. W; are 
not aware that Mr. Wanklyn has replied to the objections 
to his method, but we observe that he still adopts it in his 
determination of the organic contents of doubtful waters. 
The best, easiest, and safest method of estimating organic 
matter is, no doubt, the great problem to be solved in water 
analysis ; but as it is not agreed whether the combustion 
process, the permanganate or oxygen process, or the al- 
bumenoid process, is the right one, it would seem reason- 
able that in all eases of dispute the analytical chemist on 
each side should be expected to give his results, not only 
in the way he thinks best, but also in the terms adopted by 
his confrere, and in such form that they admit of immediate 
comparison. If no other agreement can be arrived at, we 
may at least expect so much, and we think that in time it 
might be found possible to obtain, by common consent, a 
middle way that should satisfy all parties. At any rate 
and first of all, there might be a consensus in the matter of 
arithmetic. 
The Fly-trap— Its First Discovery. — The Fly-trap 
( Dioncea muscipula) has lately been much spoken of ; so it 
will be interesting to learn when this plant was first made 
known. John Ellis (1711-1776), a London merchant, re- 
ceived in 1769, from Philadelphia, the plant, and described 
it with drawings in “ Directions for bringing over Seeds 
and Plants from the East Indies and other Distant Coun- 
tries in a State of Vegetation, to which is added the Figure 
and Botanical Description of Dioncea muscipula'' London, 
1770. The same gentleman published in 1771, “ Copies of 
two letters to Dr. Linnaeus and Mr. W. Aiton,” contain- 
ing descriptions and drawings of two other North American 
plants, Illitiwn Jloridanum and Gordonia lasianlhus. 
Fred. Brkndel. 
