_ £eb. 2, 1882] 
NATURE 
313 
Turnford, Kentish Town, and Tottenham Court Road ; 
and thus only six or eight more borings would be neces- 
sary. With the improved methods of working by the 
diamond rock-drill, these borings could probably be 
carried to the depth of 1000 feet at the cost of a few 
thousands of pounds, and this would be a very moderate 
sum to pay for settling such a highly important question. 
It is of course possible that only two or three of these 
borings would be required, and the order in which they 
should be executed must be in a great measure deter- 
mined by the results which were obtained by those first 
put down. Probably it would be well to commence with 
the sites suggested by Prof. Prestwich and Mr. Godwin- 
Austen respectively, namely, Croydon or Sydenham, and 
a point near the North Downs. 
The only chance of this line of borings missing the coal- 
bearing strata would result from the circumstance that the 
‘coal-troughs are not continuous, but are, in all probability, 
like those of Belgium and Northern France, separated by 
pre-Cretaceous upheaval and denudation, along lines cross- 
ing the great axis, into separate long and narrow basins. 
It is therefore just possible that a boring might reach a 
point lying between two such basins. It would follow 
‘from this that while the Coal-measures, if they exist, 
would in all probability be found by such a systematic 
search as we advo@ate, yet the failure to discover them 
would not absolutely demonstrate their absence in the 
whole of the Metropolitan district. 
Since it is the people of London who would mainly 
benefit by the discovery of coal under their city, it is by 
them that the effort to raise the comparatively moderate 
sum of money required for such a systematic search as 
we have advocated must be made. When the magnitude 
of the interests at stake is remembered, it is surely not 
too much to hope that, so soon as the people of this city 
fully realise the importance of the evidence brought for- 
ward by geologists, they will be prepared to make the 
necessary effort to secure the decision of the question in 
the only way that is practicable, namely, by actual 
experiment. 
Some of those who have recently engaged in this dis- 
cussion have taken it for granted that the great smoke- 
pall that too often rests over this city would necessarily 
_be increased by the discovery of coal beneath London. 
They have therefore stigmatised geologists as “ Philis- 
tines,” resolutely bent on destroying all the little “sweet- 
ness and light” left to the unfortunate inhabitants of 
London. But it is by no means certain that any such 
effects would follow from the discovery of coal in the 
metropolitan area, It must be admitted that the beautiful 
landscapes of our home counties would not be improved 
if coal-tips, engine-houses, and winding-gear were to rise 
in all directions about them, but the reduction of coal and 
gas bills to one-half or one-third of their present amount 
would, by most London householders, be regarded as a 
sufficient compensation for such disadvantages. Judging 
from the character of the coals found in the Bristol 
and Somerset and the Belgian coalfields, it is probable 
that while gas- and caking-coals would not be wanting, 
a great part of the coal under London would prove 
to be anthracite and hard coals. Every one who has 
visited the Smoke Abatement Exhibition must be con- 
vinced that there is a great future for such varieties 
of coal. The people of London who are reluctant to 
alter the construction of their grates so as to adapt them 
to the use of such coals, at their present prices, might 
find it well worth their while to do so if those prices were 
reduced to one-half or one-third of what they are at 
present. 
In this way the discovery of coal under London might 
lead the way to that general reform in our domestic hearths, 
which we all desire, but which we find it so difficult to 
realise; and thus, perhaps, the discovery of coal at a 
moderate depth beneath us, paradoxical as the sugges- 
tion may appear, may lead to the purification of our 
London atmosphere. JOHN W. JuDD 
THE ENCYCLOP4DIA BRITANNICA 
The Encyclopedia Britannica. Ninth Edition. Vol. 
XIII. %Inf.—Kan, (Edinburgh: A. and C. Black, 
1881.) 
T is impossible to refer in detail to all the leading scien- 
tific articles in this volume ; we can only express our 
satisfaction of the admirable manner in which the publi- 
cation keeps to the level of its first promise. We have 
only space to refer to one or two articles, regretting that 
those on ‘‘ Instinct,” by Mr. Romanes ; “ Insectivorous 
Plants,” by Mr. P. Geddes; “Iron,” by Dr. Alder 
Wright; ‘‘ Kangaroo,’’ by Prof. Flower, and others of 
equally high mark, can only be referred to. 
In Mathematics the gizéce de resistance is a very 
carefully digested article upon the J/y/inttesimal Cal-- 
culus, by Mr. B. Williamson, F.RS., who has already 
won his spurs in this field by his two treatises on the 
Differential and Integral Calculus. In a former notice 
we expressed ourselves somewhat hesitatingly upon the 
utility of elaborate articles upon branches of mathematics 
in a work of this kind, but the “Calculus,” we think, lends 
itself more readily to such treatment than almost any 
other branch. Certainly the subject, in the hands of Mr. 
Williamson, is handled in such a way that the student, so 
far as the text is concerned, will be independent of any of 
the usual textbooks, and will only require to consult themr 
for exercises to try his hand upon, to test his acquaint- 
ance with the principles herein so clearly unfolded and 
aptly illustrated. The advanced mathematician also will 
find not only sufficient matter for his purpose, but, what is 
more serviceable to him, a ready means of reference to 
the original sources of information. In this respect we 
cannot speak too highly of the care bestowed on all parts 
of the two divisions into which the Infinitesimal Calculus 
bifureates. The narrative of the contributions of Le- 
gendre, Gauss, Abel, and Jacobi to elliptic functions, in 
the concluding portion of the paper, is an admirably 
lucid exposition of the relative positions of these great 
analysts in this department. Mr. Williamson devotes 
120 columns to the practical portion of his article : in 
these he naturally treads on the lines he has pursued in 
his previous works. He follows the subject of Envelopes 
with a sketch of Symbolic Methods, first started by Arbo- 
gast, who was succeeded by Francois, Servois, and in 
more recent times by Hargreave, Boole, and Crofton. 
He gives useful reference here also to Hankel and Grass- 
mann, who have treated symbolic methods in a compre- 
| hensive manner. Another novel section in this connection 
