RECENT DREDGING IN CATTEWATER. 
399 
readily enough when tilted over the shute carrying it into the 
hopper barge ; but as the machine bit deeper into the fundus the 
character of the silt appeared to change, and it clung with such 
tenacity to the buckets that much of it slipped overboard after 
passing the shute, and some buckets would carry round their 
burdens for several revolutions of the ladder, so tightly was the 
material lodged in the same. The deeper the digging the more com- 
pact and tenacious it became, until at times as much as fifty per 
cent, would slip overboard, involving double labour in going over 
the same ground again, and bringing to the surface for the second 
time the loosened and redeposited material. 
The colour of the silt was dark slate, and so tenacious that it 
appeared to consist largely of clay. On drying the colour became 
greyish, and the material was so fine that, rubbed between the 
finger and thumb, it had all the characteristics of precipitated 
chalk. Under the microscope it was readily seen that the bulk of 
the material was extremely fine granite sand — quartz, mica, and 
felspar — and thinking it might have some small commercial value, 
I forwarded a sample to Messrs. Chance, the eminent glass manu- 
facturers, who informed me that it was not suitable for their 
purposes. I tried brickmakers as well, but they replied that they 
possessed better materials nearer at hand. 
The chemical examination disclosed the following composition : 
Sample dried at 100° C. (212° F.). 
Per cent. 
Organic matter and loss on ignition . . . 10*13 
Silica Si0 2 as sand . . . .48*45 
Silica combined, and as silicic acid . . .8*75 
(Total silica, 57*20) 
Iron-ferric oxide Fe 2 0 3 . . 4*13 
Alumina Al 2 0 3 .... 10*50 
Lime CaO . . 8*33 
Magnesia Mgo . . . . 1 *63 
Alkalies, carbonic acid, &c. . . 8*08 
100*00 
The principal peculiarity is the very fine state of the subdivision 
of this material, samples of water with the silt in suspension taking 
many clays to settle and clear. A sample of the silt amounting 
only to 0*05 per cent, was shaken in salt water ; it partially cleared 
