COLLECTION OF PLANTS FROM ASSAM, 
569 
The vel ocity of the spontaneous evaporation 
under the fierce sun and scorching winds of 
the western desert, is well exemplified by 
specimens A 15, the bacheh or infant crystals 
of one day’s growth, through 16, 17, 18, to 19, 
the 8th day’s produce ; in the last the crystals 
are cubes of full half an inch base. Again 
we find crystals of the same size in No. 22, 
from the evaporation of 8 out of l2 fingers’ 
depth of water in 20 days of the hottest season. 
In No. 23 the crystals from 6 inches depth of 
water are of | inch base. The size, however, 
of the crystals depends greatly upon the un* 
disturbed continuation of the process, and 
does not give us a clue to the quantity of salt 
deposited from a given depth of water, whence 
we might calculate the saltness of the lake 
itself at various periods of the season. The 
rate of evaporation itself may be estimated 
from the above data tolerably well ; thus — “6 
fingers in 8 days” — “ 12 fingers in -0 days” — 
will be nearly half an inch in depth per diem ! 
The pits dug for the reception of the brine 
seem sometimes to be very deep, 10 or l2 feet ; 
in these when deserted the deposit proceeds 
for several years, forming solid strata of salt 
separated by a streak of earth washed in dur- 
ing the rainy season. The accumulation is 
then dug out in mass; but in general the salt 
for sale is collected as it forms in the brine 
pits in a granular state, by which means it is 
freed from the more soluble salts witli which 
it is accompanied. The pakkd salt of the 
byopdrts or traders (Nos. 25,26), is of a large 
grain, -the latter indeed in half-inch crys- 
tals, — and not very clean. 
A circumstance of chief importancseolicited 
by Lieut. Conolly’s specimens, is'the pre- 
sence of the carbonate and sulphate of soda 
inconsiderable abundance among the saline 
products of the Samkhur lake. The greater 
f rart of the substance described by the manu- 
acturers as refuse or scum, which is stated to 
be thrown away as useless, turns out on ana- 
lysis to be carbonate of soda, contaminated 
with sulphate and muriate; and it is well de- 
serving of inquiry, whether the discovery of so 
•xtensive a store of natron in a state of great 
purity, may not be turned to profitable ac- 
count. In all the strata cut from the neglect- 
ed kiydrs the carbonate is seen overlying the 
mixed sulphate and muriate, of an efflorescent 
snowy consistence. Sometimes the formation 
of the salt is prevented by its abundance (as 
in A 4,5,6); No. 5 I find on analysis to 
contain 40 per cent, of carbonate, with 30 of 
each of the other salts-and a little care in 
separating the crystals of these would leave 
it nearly pure. 
Spicular crystals resembling nitre are seen 
in some of the specimens (All); they bear 
0 very small proportion to the general mass. 
It is but necessary to refer to Mr. Stephen- 
son’s examination of other specimens, to form 
a clear idea of the conditions best suited for 
the separation and collection of the different 
salts; thus in the old deserted pits ( B No. 1), 
the sulphate is obtained nearly pure ; in A 
6, 10, it is mixed with carbonate ; in A 5, the 
latter predominates. As for the muriate, from 
its inferior solubility, this salt is readily sepa- 
rated in a state of purity from the brine. 
The small proportion of lime in the earthy 
residue of A I, from the bed of the lake, 
rather militates against the expectation enter- 
tained by Lieutenant Conolly from native 
report, of a subjacent stratum of this mineral „ 
'i’he points now wanted to complete Lieute- 
nant Conolly’s description of the Sambhur 
salt manufacture, and the questions naturally 
induced from the information he has already 
given, are : 
1. A topographical account of the lakes, 
their extent, general depth, position relative- 
ly to adjacent plains, sands, or hills. 
2. The extent of the manufacture, produce, 
possible increase, price, and other statistical 
data. 
3. Whether the carbonate and sulphate 
are worked and used? the quantity and price 
of these. 
4. The exact process followed by the na- 
tive manufacturers or collectors. 
5. The specific gravity of the water, both 
of the lake and of the brine pits, at different 
seasons ; which may be found in the absence 
of the means of determining it on the spot, 
by bottling off a portion at stated times. This 
would also enable us to ascertain whether the 
carbonate existed in the water, or whether u 
was formed during the evaporation, by the 
action of the lime or other eartlis. The pre-^ 
senceof magnesia, of potash, and of iodine^ 
also remains an undecided point, as well as 
the nature of the pink or amethystine colour- 
ing matter remarked in some of the speciioens 
(A No. 24). 
To conclude this hasty note. I may men- 
tion that I have found M. Gay Lussac’s 
alkalimeter a very convenient instrument 
for examining these mixed salts. By prepar- 
ing three standard bottles of dilute nitric 
acid, nitrate of barytes, and nitrate of silver, 
adapted to his centesimally-divided dropping 
glass, the per centage of carbonate, sulphate, 
and muriate, is obtained successively from the 
same specimen with great ease and rapidity.” 
Another valuable paper is from Mr. 
Griffith, on a collection of plants from 
UPPER ASSAM. 
The plants collected amount to about 1500, 
which may be considered about one-fourth 
of the Flora. The portion of Assam seen by 
Mr. Griffith may be compared to an exten- 
sive plain, intersected in various manners by 
belts of jungle , the breadth of which is not 
very great, and towards the eastern boun- 
dary the spots unoccupied by jungle 
become fewer and less spacious. Between 
Kujoo Ghat on the Noa Dehing, and Nun- 
groo on the Booree Belling^ and in the whole 
of that direction, the country is occupied 
with jungle. Mr. Griffith’s collection wait 
