Scientific Intelligence.— Geology. 181 
by the agency of steam, applied to this new invention. The slow 
and expensive process of perforating by the drill and blast will be 
thrown aside. In the trial experiments the machine, moved by a 
steam-engine, cut an excavation of seventeen feet in diameter 
through the hardest rock at the rate of about three feet in two hours. 
The process consists in cutting and crushing the rock by means of 
rotating discs of steel, in successive series, which describe in their 
movement segments of circles from the centre to the circumference 
of the tunnel, with a gradual motion around the common centre ; 
while the steam-engine is constantly pressing the machinery on a 
direct line with the axis of the tunnel, The newest and most extra- 
ordinary feature of the application of this power consists in the com- 
bination of different sets of discs, which act upon the entire surface 
‘to be excavated by a system of gradation perfectly regular, and by 
a power that is irresistible. The machine, which worked most sa- 
tisfactorily, is made entirely of iron, and weighs about seventy-five 
tons, exclusive of the engine and boiler. One of the most interest- 
ing features of the experiment was when the machine began to cut 
the rock in an oblique direction, for it was observed that those discs 
or arms which were cutting the stone moved with the same facility 
that those did which were playing in the air.. Gradually the cutters 
‘described their curve, the great faceplate of seventeen feet constantly 
revolved, throwing out and drawing back its arms with complete re- 
gularity, seizing and crushing the rock with irresistible power, Only 
four men are required to work this machine to the greatest advant- 
age; and two of them confine their attention to the engine which 
propels it. There is no necessity for suspending the work day 
or night, except for those intervals when the cutters have to be 
‘sharpened, or new ones substituted. The amount of time and ex- 
pense which is saved by the operation is almost incredible. This 
machine evidently supplies a want which has been felt in every de- 
partment of civil engineering. It will revolutionise the whole sys- 
tem of railway construction, and is regarded as one of the most won- 
derful inventions of f any age. 
11. Fable of Statistics respecting the Mississippi, by Mr Brown. 
1. Quantity of water discharged by the Mississippi river annually. 
14,883,360,636,880 cubic feet. 
2. Quantity of sediment discharged by the Mississippi manually, 
28,188,083,892 cubic feet. 
3. Area of the Delta of the Mississippi, according to Mr Lyell, 
13,000 square miles. 
4, Depth of the Delta, according to Professor Riddell, 1, 056. 
_§. The Delta, shecofaata, according to 3 and 4, as above, contains 
400,378,429,440,000 ae feet, or 2,720 He miles, 
6. According to 2 it would require, for.the formation of one cubic 
mile of Delta, five years and eighty-one days. 
