504 
NATURE 
| March 29, 1883 
tions. All the more welcome will be this pleasantly 
written volume, which gives a far brighter picture of the 
Republic and its prospects than its most sanguine sym- 
pathisers may have anticipated. Since the expulsion of 
the French in 1867, profound peace has prevailed both at 
home and abroad, interrupted only by a few feeble and 
aimless pronunciamientos in the years 1868 and 1869 ; 
signs of moral and material progress are everywhere per- 
ceptible ; security for life and property is being extended 
from the capitals to the remotest districts of the several 
states ; the whole country is already covered with a net- 
work of railways connected in the north with the United 
States system, and affording several alternative routes be- 
tween the Atlantic and Pacific Oceans ; lastly, the Liberal 
party, which has guided the destinies of the Republic for 
over twenty years, has succeeded in establishing free 
institutions on a firm basis. “I have every confidence,” 
writes our author, “that the favourable terms in which I 
have spoken of the country will not hereafter be found to 
be exaggerations ; that my ideas as to the future prosperity 
of Mexico being early realised are true, and that such 
ideas are held by most of its leading men.” And he adds 
that the time has come for England to bring about “a 
reconciliation with a country, in whose aid her influ- 
ence and power could be so beneficially exerted’’ 
(p. 259). f far Nn ; 
The contents of this work, which is sumptuously illus- 
trated by no fewer than fifty-six coloured and other 
plates from sketches by the author, are extremely varied, 
special chapters being devoted to the present state of the 
capital and surrounding districts, to the public institu- 
tions, the Roman Church, Protestant missions, trade, 
manufactures, farm life, the Pachuca silver mines, anti- 
quities, the ruins of Teotihuacan, the remarkable lime- 
stone caves of Cacahuampila, Popocatapetl, and many 
other topics of general interest. During the ascent of 
Popocatapetl, the traveller ascertained that, according to 
the latest survey, the edge of the crater was 19,000 feet 
above sea-level, the usual estimates being 17,850 to 17,880, 
and that the peak still rose 1000 feet higher. Should 
these calculations be confirmed, Popocatapetl will again 
take its place as the culminating point of North America, 
a position from which it had recently been deposed by 
Mount St. Elias on the Alaska coast! On the same 
occasion another curious discovery was made. General 
Uchoa, present owner of the crater and its rich sulphur 
deposits, told our author that the eruption of 1521, as 
described by Diego Ordaz, one of Cortes’s captains, must 
have been due to some misapprehension. All geologists 
who have lately visited the crater, or who have examined 
specimens of its minerals, are now convinced that no 
eruption can have taken place for the last 10,000 years. 
This is a great confirmation of the opinion now generally 
entertained that the underground energies diminish 
steadily in vigour as we proceed from the Southern 
Cordilleras, through Central America, northwards to the 
Anahuac tableland. The financial condition of Mexico is 
described, contrary to the current impressions, as far from 
hopeless. 
Of the numerous illustrations a large number are 
occupied with curious little clay heads, obsidian knives, 
stone pestles, arrowheads, and other objects found amongst 
the debris of the Teotihuacan ruins and elsewhere. There 
are also excellent reproductions of the famous Aztec 
Calendar and sacrificial stones, of a beautiful vase from 
Teotihuacan, of Teoyamiqui, the goddess of death, and of 
an exquisite vase of Centeotl, or the Mexican Ceres, a 
perfect gem of Aztec art. Many of the objects brought 
home by the traveller have been placed in the hands of 
Mr, Franks of the British Museum, and are no doubt 
ultimately destined to enrich the Christy collection. 
A. HK. 
t On the British Admiralty charts this mountain is marked 14,800 feet, 
but by the late United States Survey it was raised to 19,500 feet. 
LETTERS TO THE EDITOR 
[The Editor does not hold himself responsible for opinions expressed 
by his correspondents. Neither can he undertake to return, 
or to correspond with the writers of, rejected manuscripts. 
No notice is taken of anonymous communications. 
[The Editor urgently requests correspondents to keep their letters 
as short as posstble. The pressure on his space ts so great 
that it ts impossible otherwise to insure the appearance even 
of communications containing interesting and novel facts.| 
The Matter of Space? 
INE 
In the aggregations of points which form ponderable bodies, 
other means exist of suppressing the effects of the points’ attrac- 
tions for each other than the simpie counteracting forces of the 
above figure. Clausius’s equation of stationary motion in fact 
informs us that this will take place when there is no exertion of 
tractive moment, or no total instantaneous sum of motor-couple 
actions in the system. This simply appears to imply that the 
pair of orbs A, A, and the pair A,’ A, are in that case no longer 
independent of each other in their transference and counter 
transference of motor energy, but that the twofold action of such 
energy is then a self-neutrali-ing one ; or in other words that the 
energy given off at A) passes on to A,’ ; and that discharged at A,’ 
is taken up by A, ; so that in the case where B B ‘are in stationary 
motion, or combine to form a “sphere” of two gravitating points, 
or again where many such points collected together form a perma- 
nent ponderable body, orb-couples intervene between the otherwise 
free extremities, Ay'A, and A,A,’ of the two ether systems (in the 
directions shown by arrows in the figure), and bind them together 
conservatively by an endless circuit of motor enerzy through the 
ether-orbs, while a similar endless flow of ordinary momentum 
through the ponderable channels of the system in the meantime 
| constirute also the usually recognised internal, gometrical, or 
‘‘lost” forces of such a permanent aggregation, ‘‘sphere” or 
“body” of ponderable matter. 
This subjection of two or more baric points B B’ &c. to the 
condition of stationary motion, asthe bond of neutrality of ‘lost ” 
geometrical or ‘‘internal” forces between them differs therefore 
from the case before supposed of absolute suppression of all 
interforce between them in this, that when (in the latter case) 
the motions of the points B B’ &c. areabsolutely free and entirely 
exempted from disturbing force action, the motor-vigours of the 
couplets A, Ay, Ay’ A,’&c. of the ether-orbs in permanently bound 
binary attendance upon the baric points B B’, &c., respectively, 
will then also be equally exempt and free from disturbing actions 
of any other orb-couples upon them, than those only by which 
they are dually and counter-equally bound to each other through 
the channels of their respective baric centres B B’, &c. 
Throughout the whole of a baric point B or 8,’s state of un- 
disturbed rest or motion, the ether-couplet attached to it is con- 
stantly transmitting from one of its ether-orbs to the other a 
ceaseless flow of undirected energy, or it is etherially exercising 
a ceaseless undirected horse-power, whose supply of energy is 
drawa from and is returned again without mal-destination to the 
universal ether’s general stock of energy, if the meaning of the 
principle of conservation of energy in this case may be said to be 
that, for the entire sum of all its parts, the universal ether’s whole 
stock of energy never undergoes any alteration. We may next 
consider also: the case where the interforces between baric points 
are not entirely absent, but may present us with a resultant alge- 
braic sum of any number of interforces, instead of with a neutral 
sum only of two equal and opposite ones. Although in that 
case there is no counter-equality between the motor-couples 
which act on the ether cortége A, A, &c. of each baric point B or 
B &c. yet if the motions of these latter points are subjected to 
no condition of stationariness under the influence of the forces 
acting on them we may yet recognise the universal ether’s whole 
* Continued from p. 460. 
