SCIENTIFIC SUMMARY. 
213 
are dispensed with. The ordinary slide valve is enlarged, and by an inge- 
nious arrangement the ends of the valve, in its travel, project beyond the 
ends of the valve chest, so as to expose a gas jet, contained in a cavity of 
the valve. This jet is lighted at a fixed burner, and at the return of the 
valve ignites at the proper moment the mixed gases in the cylinder. M. 
Hugon introduces a jet of water into the cylinder at the instant of explosion 
which by its instantaneous evaporation diminishes the intensity of the tem- 
perature, keeps the cylinder cool, equalizes the pressure and assists in lubri- 
cation. He also provides separate pumps for maintaining the supply of the 
explosion compound and the gas for the exploding jets, at the requisite 
pressure. 
S 'team Rollers . — One of the great steam rollers recently introduced in 
Paris has exploded in the streets with fatal results. 
Chilled Shot . — A controversy has arisen between Mr. Nasmyth the well- 
known inventor of the steam hammer, and Capt. Palliser as to the invention 
of chilled shot. Mr. Nasmyth, it appears, proposed cast-iron chilled shot, for 
penetrating armour, at the meeting of the British Association at Cambridge, 
in October 1862. Capt. Palliser, on the other hand, claims that the ogival- 
fronted form of his shot is an equally important part of the invention as the 
material of the shot. And he has certainly been the first to show how 
shot of suificient hardness could be obtained, by the use of a particular 
quality of iron, and to demonstrate practically their effectiveness against 
iron armour. On the other hand, Mr. Whitworth, in a letter to the Times , 
whilst admitting the penetrative power of the ogival-fronted cast-iron shot 
when striking the target perpendicularly, still maintains that they are useless 
when striking obliquely, and that sound well-tempered steel shell with flat 
fronts are the only projectiles to be relied on under the varied conditions of 
naval warfare. 
Mont Cenis Railivay . — In a paper read before the Institute of Civil Engi- 
neers, Capt. H. W. Tyler has fully described the results of experiments with 
Mr. Fell’s locomotive, which has been adopted for surmounting the steep 
gradients and sharp curves of the Mont Cenis route. On Mr. Fell’s system 
an intermediate or centre rail is adopted, against which horizontal wheels 
worked by the engine are pressed by springs so as to yield any requisite 
amount of adhesion. The engine constructed for the Mont Cenis line is 
partly of steel ; its weight fully loaded does not exceed 17 tons. There are 
two 15-inch cylinders working both the four coupled horizontal, and the 
four coupled bearing wheels. The pressure on the additional horizontal 
wheels can be varied by the engine driver at pleasure ; during the experi- 
ments it amounted to from 2\ to 3 tons on each wheel, or 10 tons altogether, 
but provision was made for increasing this pressure to 24 tons if necessary. 
During the official trials, with a load of 24 tons exclusive of the engine, on 
an average gradient of 1 in 13, with curves of 2 to 4 chains radius, the speed 
of 6-65 miles to 7 ’46 miles per hour was attained in ascending. With a load 
of 16 tons the speed was 10 miles. 
Snow Ploughs . — In Engineering for March 1 are described and figured the 
snow ploughs which are employed by Mr. William Strandley, on the High- 
land Bailway of Scotland, for clearing a way for the trains through the 
heavy snow drifts to which that line is peculiarly liable. The largest of 
