* Fab, 20, 1873] 
formerly have extended that the lakes lie. The great depth of 
Lake Maggiore beneath the sea-level—2, 300 ft.—is no argument 
_against the theory, for a large mass of ice would block out the 
sea-waters. In Wales the lakes are never of large size, Lake 
Bala, the largest, being about 44 miles long ; Lake Windermere 
lies in a true rock basin, as do many others in that district ; in 
Scotland, where the climate was more severe, the lakes are 
larger and more numerous ; in Sweden and Norway, in Finland 
and N. Russia the lakes are almost innumerable, while in N. 
America they are scattered almost broadcast over the country 
N. of lat. 43°. Where the glacial action was most intense, there 
the lakes become more and more numerous, and he believed 
they were due not to special glaciers, like those on the south 
side of the Alps, but to that great ice sheet which, according to 
Agassiz, covered the whole country. In South America and 
New Zealand, too, are signs of a similar action, and there too, 
lakes of this class occur. ‘The present glaciers of New Zealand 
are very small compared with what they evidently were at a 
previous’period, and in the course of every one of them are lakes, 
which, according to reports he had received, also lie in true 
rock basins, 
II, SALT WATER LAKES, THEIR ORIGIN AND 
GEOGRAPHICAL DISTRIBUTION 
The lecturer said that he could not account for the origin of 
all salt-water lakes, but for some of them the evidence is clear, 
and it is plain to see why they are salt. The principal minerals 
forming the rocks of the earth’s crust are silica, alumina, lime, 
potash, soda, magnesia, peroxide of iron, &c. — Rain-water 
takes up from the atmosphere and the earth’s surface a small 
proportion of carbonic acid, and thus acquires the power of 
dissolving certain of these minerals as it percolates through the 
rocks, notably lime, which it carries away in the form of a bi- 
carbonate. And thus the water of all springs is charged more 
or less with mineral ingredients, though these may be recog- 
nisable only by the skill of the chemist. Thus the water of the 
fountains in Trafalgar Square contain 69°75 grains of salts per 
gallon, including chloride of sodium 2577 ; bi-carbonate of soda 
14°5 ; sulphate of soda 18°4. The Thames water at Teddington 
contains 22°5 grains per gallon, and thus carries to the sea in the 
course of a year 377,000 tons of salts; the old well at Bath 
holds 144 grains of salts per gallon, thus bringing to the surface 
608 tons of salts per year. The apparently small quantity of 
bi-carbonate of lime in a per-centage of the salts of sea-water, 
is still sufficient to furnish to marine creatures materials for their 
shells and skeletons, and thus indirectly to build up the great 
beds of limestone which are now in course of formation, or 
belong to former geological periods. The analyses of salts in 
sea-water andin the water of various lakes is given in the 
following table : 
Mediter- Black Seaof Caspian Dead 
Per centage of ranean Sea. Sea. Azof. Sea. Sea. 
Chloride of Sodium..... 2°9460 14020 09658 0 3673 12°110 
ra Magnesium 0°3223 0'1304  0°0887 00632 7822 
= = = = 2455 
a 070505 oor oo128 070076 1217 
Bromide of Magnesium — 00005 O0004 trace 
Sulphate of Lime .......- 0°1357 070105 0'0288 00490 
Ep Magnesium "2480 0°1470 0°0764 01239 
Bromide of Sodium .... 0°0558 -_ = _ 0'452 
Carbonate of Lime...... o"oIr3 ©0359 0'0022 o’or7r 
cH Magnesi: - 07020} 00129 00013 
Peroxide of Iron... 070004 — a a 
3°7700 1°7661 11880 0°6294 24°056 
Salt lakes though not so numerous as fresh-water lakes, occur 
in large numbers in certain regions. The Caspian Sea with an 
area as large as Spain, the Sea of Aral, and a vast number among 
the mountains and table-lands north of the Himalaya; the Dead 
Sea in Syria; L.Utah,and neighbouring lakes among the moun- 
tains on the western side of North America; and among the moun- 
tains of South America and in the interior of Australia are ex- 
amples of large salt water lakes. It will be noticed that all these 
lakes lie in an area of inland drainage, that they have rivers 
ranning into them, but that they have no outlet. On inspecting 
the above table it will be seen that the Black Sea is fresher than 
the Mediterranean, by reason of the greater supply of fresh water 
-furnished by the rivers, and Edward Forbes showed that this 
freshening has caused certain of the shells of Mediterranean 
species to assume “monstrous” shapes. The Caspian is'stiil fresher, 
and its fauna and fossils in recent deposits in the neighbourhood 
prove it to have once had connection with the Black Sea, from 
which it has been separated by changes in physical geography ; 
it was then salter than at present, but is now growing salter 
P Fy ree Ne ee, | 
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313 
again every year, and the fauna now inhabiting its waters 
have likewise considerable affinities with North Sea types.’ 
Its surface level is -83°5 ft. below that of the Black Sea, 
while the surface of the Dead Sea is 1300 ft. below that of 
the Mediterranean. In all cases where rivers flow into de- 
pressions in the land, however these might have been formed 
(oscillating movements of the earth’s crust might perhaps form 
such large ones as the Caspian basin), carrying with them certain 
salts in solution, if the lake have no outflowing river, the water 
must. be carried away by evaporation, in which case the salts 
will be left behind, and the remaining waters become more and 
more saturated. It is stated that crystals of salt have been 
brought up from the Dead Sea, and on the shallow waters on its 
coasts evaporating in summer saline incrustations are left. The 
same water which flows ¢hrough the Sea of Galilee, a fresh- 
water lake, renders the Dead Sea one of the most remarkable salt 
lakes in the world. And in this and all similar cases accumulation 
of salts will go on till the saturation point is reached, and 
then precipitation will commence. The region to the north of 
the Himalayas is comparatively rainless, owing to the mountains 
condensing the moisture carried by the south winds, and the 
rivers consequently do not carry into the lakes sufficient water to 
make them overflow their boundaries, hence they are salt. Lake 
Baikal, with an outlet to the sea, is quite fresh. For a similar 
reason the moisture from the south-west winds being condensed 
in great part by the Sierra Nevada, the lakes which lie in the 
great plains and table-lands to the east of that range have not a 
sufficient supply of water to cause them to overflow, and conse- 
quently they are salt, and are continually becoming salter. In 
Ioo parts by weight of the water of the Great Salt Lake in that 
region, there are of chloride of sodium (common salt) 20°196 ; 
sulphate of soda 1°834; chloride of magnesia 0°252; chloride 
of calcium a trace, making a total of 22°282. And by means of 
the old water levels in the form of terraces round its margin, 
it can be proved that it has shrunk very considerably, and there- 
fore its salts must be becoming very much concentrated. On the 
surrounding plains a saline efflorescence is found, which the 
lecturer believed might be explained by the rain which saturated 
the rocks during the rainy season rising again to the surface 
charged with salts dissolved from the rocks, during the intenss 
heats of summer. 
(Zo be continued). 
SCIENTIFIC SERIALS 
THE Zovlogist for January and February contains reviews of 
the works of Capt. Shelley and the late C. J. Andersson. Dr. 
Gray contributes a paper on the Cetacea of the British Seas, 
and Mr. Harting has a supplement to his paper on the British 
Heronries, a subject on which there are several letters also 
published. Messrs. Stevenson and J. H. Gurney, jun., send 
Omithological notes from Norfolk, and Messrs. Gatcombe and 
Cordeux from Devon and Lincolnshire respectively. 
Tue Entomologist for January and February, among other 
articles of interest, contains one by Mr. H. C. Lord, on ‘‘ The 
Lepidoptera of Switzerland,” as far as could be obtained in a 
twelve days stay. Out of the sixty-three species of butterflies 
met with, twenty-four are not British. Many of the English 
commonest forms are among the most frequently found there. 
Colias Hyale is commoner in some parts than C. Zdusa, and C, 
Helice is not unfrequently found. Mr. F, Walker continues 
his papers on ‘‘ Economy of Chalcidiz.” 
SOCI-FTIES AND ACADEMIES 
LONDON 
Royal Society, Jan. 9.—‘‘ On a new Method of viewing the 
Chromosphere,” by J. N. Lockyer, F.R.S., and G. M. Seabroke. 
The observations made by slitless spectroscopes during the 
eclipse of December 11, 1871, led one of us early this year to the 
conclusion that the most convenient and labour-saving contriv- 
ance for the daily observation of the chromosphere would be to 
photograph daily the imaye of a ring-slit, which should be coin- 
cident with an image of the chromosphere itself. 
The same idea has since occurred to the other. 
We therefore beg leave to send in a joint communication to 
the Royal Society on the subject, showing the manner in which 
this kind of observation can be carried out, remarking that, al- 
though the method still requires some instrumental details, which 
