NATURE 
[ Fan. 20, 1870 
DR. BALFOUR STEWART'S METEOROLOGICAL 
BLOCKADE 
| MAGINE a line drawn round any district, and consider 
all the air that passes over that line outwards and 
inwards in any time. Let the whole quantity of vapour 
of water carried across the boundary line by this air be 
determined. If during any particular interval of time 
there is just as much vapour carried outwards as inwards, 
there must be in that interval either no rainfall on, and 
no evaporation from the district, or there must be just as 
much rainfall as evaporation. If more vapour is carried 
out than in, there must be more evaporation than rainfall. 
Or, if more vapour enters than leaves, the difference falls 
in excess of rain above evaporation. : 
Dr. Stewart proposes to establish a cordon of meteoro- 
logical stations, and to arrange a reduction of observations 
taken at them, so as to keep, as far as possible, an exact 
account of the quantity of vapour entering and leaving 
the space over the surrounded district. This appears to 
meamost valuable proposal, which, if well carried out, 
must have a very important influence, tending to raise 
meteorology from its present empirical condition to the 
rank of a science. The object of the present notice is to 
suggest that the same system of account-keeping ought 
to be applied to electricity. 
Whatever we may think as to the nature of electricity, 
it certainly has, in common with true matter, the 
property of being invariable in quantity. This property 
is conveniently enough expressed, as it were, mechanically, 
" by the one-fluid hypothesis, which asserts that positive or 
negative electrification of any piece of matter consists in 
the presence of more or less than a certain quantum of 
the electric fluid; that quantum being the amount 
possessed when the matter in question exercises no at- 
tractive or repulsive force, varying with artificial variations 
of the electric condition of the testing body presented to it. 
On this hypothesis, “ quantities of electricity,” positive and 
negative, are excesses of the quantity of the hypothetical 
fluid above or below the “ quantum” corresponding to 
zero of the electric tests. 
The ordinary fair-weather condition in our latitudes 
presents us with negatively electrified air in the lowest 
stratum, extending at least as high as our ordinary houses 
above the surface of the earth ; and positive electricity of 
greater amount, on the whole, in the higher regions. The 
atmospheric electrometer indicates in absolute electrostatic 
units the total quantity of electricity in the atmosphere, over 
a certain area of the place of observation ; being the excess 
of the amount of positive above the amount of negative 
electricity inthe whole column. This excess in fair weather 
is generally positive. The fact that it is not the electricity in 
the lower regions. alone, but an effect depending on the 
whole electricity of the atmosphere from lowest to highest, 
that is the thing observed in the ordinary observation of 
atmospheric electricity, renders this subject more suitable 
even than moisture for the application of Dr. Stewart’s 
blockade. ‘Thus, the hygrometrical blockade is complete 
only if both moisture and the effective component of wind 
are known at all heights above the surface ; the electrical 
blockade is complete when, besides the electrometer 
measurements at the observatory, the effective component 
of the wind at all heights is known. But among the many 
| unknown quantities involved, the tivo departments of the 
blockade combined will give means for eliminating some 
and estimating others for which the hygrometrical blockade 
alone, or the electrical one alone, would be insufficient. 
WILLIAM THOMSON 
THE SCENERY OF ENGEAND AND WALES 
The Scenery of England and Wates, its Character and 
Origin. By D. Mackintosh. (Longmans and Co.) - 
|PBAEIESS of some of the geological journals are 
sufficiently acquainted with the name of Mr. 
Mackintosh. They know him as a writer who, for the 
last four or five years, with wonderful perseverance, has 
kept on enunciating certain views of denudation which he 
has adopted. His papers, however, do not suggest that 
their author possesses the large grasp of the subject, 
the range of acquirement in geological studies, and the 
gifts of style which must necessarily belong to the man 
who would successfully expound the history of the scenery 
of the country. The task is a difficult one— much more 
difficult than even geologists themselves usually believe— 
and the announcement that it had been undertaken by 
Mr. Mackintosh probably took a good many readers by 
surprise. They could not but award him the credit of 
great boldness, whether or not they found, on examina-. 
tion, that he deserved also the praise of success, 
Mr. Mackintosh, as a writer on geological subjects, is 
under the influence of one dominant idea. He believes 
in the Sea, the whole Sea, and nothing but the Sea. It 
seems to haunt him like a nightmare. To his ear all 
sounds in Nature are drowned in the thunder of waves, 
the rush of ocean-currents, the beating of multitudinous 
billows, that batter and grind the solid substance of the 
land. A mist of ocean spray is ever in his eyes. He can 
but dimly see that any other powers are at work around 
him save the everlasting breakers. The fall of rain, the 
| roar of rivers, the silent majesty of glaciers and snowfields, 
have little charm for him, and can. never wean his 
affections from his first love. He can be brought to turn 
his thoughts neither to the right hand nor to the left, 
but keeps his eye stedfastly fixed on the one grand object 
of his faith and adoration. If, indeed, for a moment the 
contending claims of some other power in Nature obtrude 
too pertinaciously upon his notice, he clings to some 
bigger wave, or dashes into some stronger ocean-current 
until the temptation has passed away. 
It is seldom that we meet with one governing idea so un- 
flinchingly followed to the exclusion of anything and every- 
thing which might modify it; seldom that we encounter 
mental colour-blindness so thorough as to admit of the 
discrimination of apparently but one hue. Not merely 
does he everywhere and always reiterate that “the greater 
part of the land surface, at any given time, must present 
the form given to it by the sea,” but he traces this marine 
sculpturing down to the minutest details of contour, even 
though rains and frosts and streams seem to rise up in ~ 
protest to his face. The tendency unduly to exalt the 
power of the sea as a geological agent has always ~ 
characterised the writings of English geologists, probably 
from the greater prominence which the sea acquires in 
the eyes of islanders. But the tendency never received 
such an extreme development as it has done in Mr, — 
