No. 161.] 
87 
The filtering of clay in suspension in water,* is another cause 
now forming sandstones and conglomerates, but they are too easi- 
ly crumbled to be useful. 
Salt. Evaporation of sea-water by cords or Jagots. 
Salt is manufactured on some parts of the shore of Long Island, 
by exposing sea-water in shallow vats, to the sun and wind. 
A method of evaporating very weak brine is pursued at Mou- 
tiers, in the Alps, which, in my opinion, may be introduced with 
advantage on our coasts, and perhaps with still greater profit in the 
salt spring region. This method consists in exposing a great sur- 
face continually to the action of the winds, either by permitting 
the brine to trickle down cords attached to troughs twenty or thir- 
ty feet above the ground, leading to other troughs below; or by 
permitting it to trickle through loose brush, thrown into open frames 
of slight timber work, between the upper and lower series of 
troughs. The lower series of troughs conducts the concentrated 
brine to reservoirs. The location usually selected is on a hill 
side, where the brine, coming from one set of frames, flows direct- 
ly into the upper conductor of another set at a lower level, the top 
of which is on a level with the bottom of the preceding, and from 
the second set of frames passes to a third in the same manner, un- 
til it is concentrated, nearly to the point of crystallization. It is 
then boiled down and crystallized in the usual way. These com- 
'binations of frames are several hundred yards in length, with a 
breadth of a few feet. Their length is placed in a direction per- 
pendicular to that of the prevailing dry winds, in order that the 
greatest effect may be produced. The sulphate of lime, and other 
salts of moderate solubility, are deposited on the cords or brush, 
which, after a time, become coated with a solid, stony crust of con- 
siderable thickness. This method is employed at the place men- 
tioned, in evaporating water containing only one and six-tenths 
per cent of salt, with considerable profit. 8,000 hogsheads of the 
WAter are thus concentrated to 500 hogsheads, and this strong so- 
lution is then boiled down. Local circumstances must necessarily 
be taken into consideration, in calculating whether this method may 
be profitably introduced in any particular locality. 
•* 
Erratic Blocks. 
The erratic blocks of Suflfolk county are of some importance, as 
they furnish the only rocks for building and wall stones. 
