20 
SCIENCE. 
thus produced a corresponding number of secondary 
species.” 
In 1859, language of which this is an unintentional 
paraphrase, occurring in the 11 Origin of Species,” was 
scouted as wild speculation ; at present, it is a sober state- 
ment of the conclusions to which an acute and critically- 
minded investigator is led by large and patient study of 
the facts of paleontology. I venture to repeat what I 
have said before, that, so far as the animal world is con- 
cerned, Evolution is no longer a speculation, but a state- 
ment of historical fact. It takes us place alongside of 
those accepted truths which must be taken into account by 
philosophers of all schools. 
Thus when, on the first day of October next, the “ Origin 
of Species” comes of age, the promise of its youth will be 
amply fulfilled ; and we shall be prepared to congratulate 
the venerated author of the book, not only that the great- 
ness of his achievement and its enduring influence upon 
the progress of knowledge have won him a place beside 
our Harvey ; but, still more, that, like Harvey, he has lived 
long enough to outlast detraction and opposition, and to 
see the stone that the builders rejected become the head- 
stone of the corner. 
T. H. Huxley. 
WATER ANALYSIS. 
The recent publication of Dr. Frankland’s convenient 
little volume on this subject ;* the important memoir by Dr. 
Tidy read and discussed last year before the Chemical 
Society, and published in its yountal;\ and the volume 
published as long ago as 1868, and now appearing in a fifth 
edition, by Professor Wanklynand Mr Chapman, j: in which 
Dr. Frankland’s title was anticipated, contains the literature 
of a subject which has of late years assumed extreme im- 
portance, but concerning which there is a haze of mystery 
and obscurity that assuredly ought not to exist. It is cer- 
tainly very much to be regretted that there is no common 
and recognized method of procedure in this department of 
chemistry, but it is almost disceditable that not only are the 
results of analyses given in discordant chemical expressions, 
but even the figures are not in the same terms, so that a 
comparison of results is impossible without performing an 
arithmetical operaton. So long as one chemist expresses 
his results in ioo-ioooth parts, another in grains per gallon, 
and a third in milligrammes, or parts in a million ; while 
one estimates ammonia as a total, another separates free 
from organic ammonia, and the third regards the quantity 
of what is called albumenoid ammonia as of vital import- 
tance ; while one adopts the combustion or evaporation 
method to determine the actual quantity of organic contents 
of water, and another accepts the permanganate method to 
discover the quantity of oxygen required to oxidize the 
organic matter present ; it is evident that the comparison of 
analyses affected by the pupils of the various schools cannot 
be satisfactory or conclusive, because they cannot be com- 
pared. Surely the time has come when methods of analysis 
giving the quantity of organic carbon and nitrogen and its 
condition or history in some intelligible form, the quantity 
of nitrogen as nitrates, the quantity of chlorine, and the 
hardness, in similar terms, should be so far agreed upon 
that results can be compared, and those who are not chem- 
ists will then be able to form some opinion as to facts. We 
believe all our most distinguished chemists would agree that 
this is possible. It only needs that each should give way in 
some matters that are not essential, but rather belong to the 
* “ Water Analysis for Sanitary Purposes, with Hints for the Interpre- 
tation of Results.” By E. Frankland, Ph.D., F. R. S., &c. London : 
Van Voorst. 1880. 
+ “ The Processes for Determining the Organic Purity of Potable 
Waters.” By C. Meymott Tidy, M.B. Journal of the Chemical Society , 
Jan., 1879. 
f “ Water Analysis : a Practical Treatise on the Examination of Potable 
Water.” By J. Alfred Wanklyn, M.R.C.S., and Ernest Theophron Chap- 
man. London : Thrlibner & Co. Fifth Edition. 1879. 
individual. Dr. Tidy well and properly observes in his 
paper {Journal of the Chemical Society, Jan., 1879): ‘‘I am 
afraid the public have taken note and are taking note of 
chemists’ differences, and distrust our work accordingly. 
Nor indeed is their distrust to be wondered at, deeply as it 
is to be lamented.” 
In Dr. Frankland’s book we find stated, in a compact 
and convenient form, the requirements of a water analysis, 
and in an appendix examples of typical analyses. He be- 
gins by pointing out the fact that complete and ultimate 
analyses are by no means called for in ordinary cases. He 
points out the unimportance, in a sanitary sense, of the 
dissolved gases, which vary but little in waters of very dif- 
ferent kinds, and of which the presence of a smaller or 
larger quantity does not affect the goodness of the water ; 
the difference, in fact, lying chiefly in the quantity of car- 
bonic acid. The separate estimation of the quantity of 
each of the saline matters and of each organic constituent 
ol the suspended matters, may in like manner, and for the 
same reason, be omitted. The processes adopted to deter- 
mine the quantities of inorganic solids, the ammonia, the 
chlorine, the nature of the hardening ingredients, and the 
presence of poisonous metals, if any, are those which are 
really important, and a knowledge of them and of the 
amount of nitrates, and lastly, but of chief importance, the 
means of estimating approximately the proportion of the 
organic elements in a sample of water, are the objects of 
which attention is really required, and to the elucidation to 
which the volume is dedicated. Professor Frankland con- 
siders that there is no process, short of the actual combus- 
tion of the organic matter present in water, which affords 
thoroughly trustworthy evidence of the organic carbon and 
nitrogen, and of the fitness or otherwise of the sample for 
dietetic purposes. The “ignition” and “ albumenoid am- 
monia” he merely mentions, and evidently disregards. 
The former is described by Dr. Tidy in his memoir, and he 
considers it is not satisfactory, as failing to show that, in 
carrying out the process — (1) no organic matter is lost, (2) 
that all the organic matter is burnt off, and (3) that no or- 
ganic matter is added. Notwithstanding this, he adopts it 
in the analysis of sewerage, and thinks that in some respects 
it may be indicative, and suggestive in other cases. The 
ammonia process, described by Mr. Wanklyn as “a sort of 
combustion process, with ammonia for the ultimate pro- 
duct,” has for its object the comparative determination of 
the nitrogenous organic matter by the quantity of ammonia 
yielded by the destruction of the organic matter, this quan- 
tity being called “albumenoid ammonia.” (Wanklyn’s 
“ Water Analysis,” 5th Ed., p. 31.) Dr. Tidy has considered 
in detail the advantages and disadvantages of this m ethod 
and has given some remarkable illustrations of its failure 
in important cases. He points out the very important fact 
that the quantity of albumenoid ammonia in peaty water is 
very large, although it has never been proved that such 
water is in any sense injurious ; and, on the other hand, 
that in waters regarded by Mr. Wanklyn as exceedingly 
bad, the albumenoid ammonia is almost nil. For these 
reasons apparently, as he quotes Dr. Tidy’s paper and 
gives no other reference, Dr. Frankland rejects them. 
In the commencement of this work, following Mr. 
Wanklyn in this, Dr. Frankland describes the preliminary 
considerations in water sampling, the quantity required, and 
the tests that should be applied to determine the presence 
of mineral poisons, the nature of refuse from manufactures, 
the action on soft lead, and the cause of turbidity. Having 
thus opened the subject, he proceeds to show in what way 
the total solids in solution can be best determined. To 
determine the organic contents, he prefers the combustion 
method. He describes the precautions required in eva- 
poration, and believes that “ the proportion of solid residue 
left on evaporation affords an approximate, though some- 
what rough indication of the comparative purity of water.” 
This, no doubt, is true in a certain sense, although it must 
not be concluded that waters showing a large residue are 
necessarily bad. It is with water as with many other things, 
we must be content with the best we can obtain under exist- 
ing circumstances, and absolute purity is practically 
unobtainable. A tolerably good river water at hand is often 
better than deep well water or lake water from a distance, 
though theoretically superior. 
