294 
depth of working. It will, therefore, be for mining and mechani- 
cal engineers to bring all the resources of their science to bear 
upon this difficult problem of counteracting terrestrial heat, at 
depths where it approaches the limit of human endurance. The 
Commissioners adopting 4,000 ft. as the probable limit of prac- 
ticable depth, came to the conclusion that there exists in this 
kingdom an aggregate quantity of about 146,480 millions of tons 
of available coal. If we assume that the future population of 
this country will remain constant, and that the consumption for 
domestic and manufacturing purposes, including exportation, will 
continue uniform at the present quantity, or merely vary from 
year to year without advancing, then our stock of coal would 
represent a consumption of 1,273 years. But if, on the other 
hand, we assume that population and consumption will go on 
increasing at the rate exhibited by the statistics of the last fifteen 
years, or, I might probably say, of the last fifty years, had accu- 
rate statistics been so long recorded, then the whole quantity of 
coal would, as shown by Mr. Jevons, be exhausted in the short 
space of 110 years. It will be generally admitted that the truth 
is likely to lie between these two extremes. The Commissioners 
refrained from expressing an opinion as to what the period of 
duration would actually be, but they presented certain alternative 
views of the question, resulting in periods varying from 276 to 
360 years. But, all these estimates of duration have reference 
to the time required for absolute exhaustion of available coal, 
and leave untouched the important question of how long we are 
likely to go on before we become a coal-importing instead of a 
coal-exporting country. The computation of quantities made by 
the Commissioners, includes all coal seams exceeding 1 ft. in 
thickness, whatever the quality may be, and it is obvious that 
vast quantities of such coal can never be worked, except at a 
price which would render it more advantageous to purchase coal 
from abroad than to work it from such unfavourable beds. If, 
at the present time, while working our best and most available 
coal, our markets will barely exclude the coal of Belgium, what 
will be our position when driven to inferior coal more costly to 
work? If we Jook to cheaper labour for enabling us to work 
less valuable coal, I fear we shall look in vain ; but there is one 
hope for a longer endurance of our prosperity as dependent on 
our coal, and that hope rests on the skill and perseverance of 
mining and mechanical engineers, who, even now, are called 
upon to lessen, by all the resources of mechanical science, the 
amount of human labour required in coal mines. 
SCIENTIFIC SERIALS 
THE Monthly Microscopical Fournal.—The first paper is 
one of Mr. Parker’s excellent siudies, being on the osteology 
of the head of the sparrow-hawk, The first paragraph 
contains a generalisation which will surprise many orni- 
thologists, for the Cariama is included among the raptorial 
birds; is this a result of the study of the skull? ‘The accom- 
panying drawings are excellent.—Dr. Royston-Pigyott gives 
two articels, ‘Onan Aérial Stage Micrometer,” and ‘‘On the 
Spherules which compose the Ribs of the Scales of the Red Ad- 
miral Butterfly, and the Lepissna Saccharina.”—An ingenious 
method of obtaining an equal illumination in both tubes of a 
binocular is contributed by Mr. W. R. Bridgman; and Mr 
Stewart endeavours to prove that the hair follicles of the negro’s 
scalp are curved instead of straight ; he also describes clearly the 
framework of the sucking feet of the Echinus.—These papers 
are followed by abstracts of intcrest, including several from the 
American journal, the Zevs, 
SOCIETIES AND ACADEMIES 
LonDON 
Royal Society, Feb. 6.—“ Memoir on the Osteology of Hyo- 
potamidze.” by Dr. W. Kowalevsky. The paper is intended to 
fill a deficiency in our knowledge of the exrinct creation by giving 
a complete osteology of one family of the Paridigitate Ungulate. 
It has been supposed thay fossil representatives of this family 
would exhibit a less reduced skeleton and a more complete 
number of digits than recent genera; yet such is not the case, 
The genera Anofplotherium and Liphodon present in their feet the 
same degree of reduction as in recent Ruminants, save the con- 
fluence in a canon-bone, Notwithstanding this, they have been 
considered the progenitors of the Ruminautia, from a deficiency 
in other forms. The present paper introduces a new form, known 
NATURE 
only by the teeth till now; these, the Ayofotamida, vary con- 
siderably in specific and generic form, ranging from the Lower 
Eocene up to the Lower Miocene period, and in size from a 
rabbit to a hippopotamus. The Eocene species, except one 
termed diplopus, have not lost the lateral digits, and are included 
in the genus /Yyofotamus. The division of the Ungulata into 
Paridigitata and J/mparidigitata mst have occurred about the 
cretaceous period, as shown by the diversity exhibited by both 
groups from the lowest Eocene. The former, the Paridigitata, 
split very anciently, perhaps in the chalk, into those with tuber- 
cular, and others with crescentic teeth. These groups, once — 
separate, kept entirely apart, but frequently followed parallel 
lines of descent, Following these two divergent lines of descent, 
both groups culminate at the present time in such forms as Pha- 
cocherus and Dicotyles for one group, and the Bovide for the — 
other, links between these being absent. The Paridigitata with 
crescentic teeth will be termed Par. selenodonta, and those with 
tubercular Par. bunodonta. To the first group belong Axoplo- 
therium, Liphodon, Hyopotamus, and others, together with the 
existing ruminants, whilst the second embraces the Swina, Hippo- 
potamina and Entelodon, There is in some cases difficulty in 
deciding whether the teeth are tubercular or crescentic, the lobes 
being so thick. 
It is important to find some osteological characters to confirm 
the above division, and the hand and foot from their variations 
suggested probable data. In tracing the Paridigitata in time, 
there is a marked tendency to the gradual reduction of the 
manus and pes, and an advantage to the individual apparently 
arises from the simplification. By comparison of all forms, a 
simple structure of the manus and pes may be obtained, such 
as was probably possessed by the common ancestor, and such a 
typeis nearly retained by Hippopotamus, and was possessed by 
Hyopotamus. In none of these forms is the limb pentadactylate, 
Supposing the feet to be pentadactylate, the following is the 
disposition of the digits in the type :— The two outer digits (the 
fourth and fifth) are always supported by one bone, the unciform 
in the manus, and the cuboid in the pes; the three succeeding 
inner digits are supported each by a separated bone, the third, 
second and first cuneiform in the pes, and the os magnum, trape- 
zoideum, and trapezium, in the manus. In the latter the third 
digit touches the unciform, and the second the magnum; the 
second digit of the pes touches the third cuneiform. The first 
digit being lost in all Ungulata, the trapezium and first cuneiform 
support the second digit. 
Beginning with this type, which was probably exhibited by 
the progenitors of the Paridigitata, the reduction along both 
lines of descent may be followed, and in doing so a series of 
parallel modifications may be obtained, though it is found among 
the crescent-toothed line thatthe reduction is much more rapid than 
along the tubercular toothed. By reduction of the foot is meant 
that locomotion is carried on by the two middle toes instead of 
by the original four ; and this seems to be an advantage to the 
organism, as it is exhibited by all descending lines of Ungulata. 
Going further into detail, it is found that both in Selenodont 
and Bunodont Paridigitata, a two-fold method of reduction of 
the manus and pes, a simple or zzadaptive, and an elaborate or 
adaftive method is observed. In the first or zzadaptive mode of 
reduction, the foot, whilst losing its lateral digits, acquires no 
better adaptation to altered circumstances of locomotion than is 
derived from the mere thickening of the remaining digits. The 
relation between the carpal and tarsal bones, and the remaining — 
two metacarpal and metatarsals, remains unaltered, and the — 
remaining digits do #ot enter into any modification by which they 
can receive more ample support from the carpal and tarsal 
bones, by taking the place formerly occupied by the reduced 
digits. Anoplotherium,  Liphodon, and Hyopotamus, are 
examples of this method of reduction, - 
In the second or adaptive method of reduction, the midile 
digits grow larger and thicker than in the first mode ; but while 
broadening transversely they du not adhere to the ancestral type, 
but tend to gain a support on a@// the bones of the carpus and 
tarsus, pushing the lateral digits tu the side and thereby gaining — 
a better and more complete support for the body. The lateral” 
digits, being rendered useless, tend to disappear, and the remain- 
ing digits, being pressed from both sides by the carpal and 
tarsal bones, tend to coalesce to form the canon bone of recent 
ruminants, or of the hind fout of Dicoty/es. In this, the adaptive 
method, modification keeps pace with inheritance, and examples 
of it may be seen in Sws, Dicotyles, Hyemoschus, and the 
Ruminants. =S 
