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POPULAR SCIENCE REVIEW. 
of chloride of calcium ; 1*388 of chloride of potassium ; 0*364 of bromide 
of magnesium ; 0*058 of sulphate of lime ; 0*004 of chloride of ammo- 
nium ; 0*032 of carbonate of lime, oxide of iron, and alumina ; 0*010 loss; 
and 79*400 of water. A litre of Dead Sea water taken on the 24th of 
February, 1862, contained 206 grammes of saline matter. There is no 
mineral water so highly charged with salts, or which possesses so much 
bromine. — Comptes Rendiis, Oct. 5, 1863. 
Fossil Fresh-water Sharks . — At a recent meeting of the Belgian Aca- 
demy of Sciences, M. Dewalque, in treating of the diluvial deposits of 
the Meuse, brought one or two remarkable facts (?) under the notice of 
the members. A few years ago, whilst some public works were being 
carried on, a large shark’s tooth was found in the gravel of the Meuse. 
He himself examined it ; it was nine centimetres long, and belonged to 
the genus Carcharodon, bearing a decided resemblance to the teeth of 
C. megalodon , which is so frequently found at Anvers that his colleagues 
thought that he was deceiving them. Now this tooth had been obtained 
by its possessor from a person who found it on the works whilst engaged 
with his pickaxe ; this, it must be remembered, occurred at a period anterior 
to the operations at Anvers. Again, M.Folie, of our School of Mines, sent 
the author some teeth which were found by his brother in the excavations 
made in connection with the citadel at Namur. They came from a 
deposit near the port of Salzinne, on a portion of flat country which 
is annually inundated, and were taken from a depth of fifty centimetres. 
One belonged, undoubtedly, to Carcharodon megalodon; four were those 
of Oxyrrhina trigonodon ; and a sixth, which probably belonged to the 
latter also, was distinguished from the rest by having its cutting edge 
slightly re-curved towards the apex. Although the sharks are marine 
species, still there are some which ascend rivers to considerable distances 
— the Lamna, for example. These facts may not be readily accepted, 
but they are worthy of the consideration of geologists. — Vide L' Institut, 
Oct. 28, 1863. 
MECHANICAL SCIENCE. 
The Steam Engine. — Considerable attention has been drawn lately to the 
question of the speed attainable in land and marine engines. Hitherto a 
velocity of piston averaging 250 feet per minute has been almost uni- 
versally adopted, and there appear to be sound objections to any great 
increase of this speed in the old form of beam engine, in consequence of 
the enormous weight of the reciprocating parts. In America, however, 
much higher speeds appear to have been attained even with beam engines, 
in cases where they had a stroke of 12 feet in length. Thus, the engines 
of the Pacific mail steamship Golden City are reported to work at a velocity 
of 420 feet per minute ; those of the Buffalo City at 468 feet ; the C. Van- 
derbilt at 540 feet ; and the Stockton at 640 feet. The objections to a 
high speed of piston which are urged with force in the case of engines 
with heavy reciprocating parts, the motion of which has to be reversed in 
direction twice in every stroke, do not apply to the class of vertical and 
