152 Progress of Invention. 



the direction of the Rev. Mr. Joyce, the incumhent, and at the 

 expense of the Duke of Wellington, the lord of the land. Un- 

 fortunately, the covering of earth over the Roman level is here very 

 shallow, in which case, as we might expect, the objects scattered 

 about are less numerous than when the covering is deep, because 

 the old floors, etc., have been longer bared to the view, and, there- 

 fore, exposed to depredation. Many Roman coins, implements in 

 iron, and other such things, have, we understand, been gathered by 

 the excavators, and the foundations, as far as yet uncovered, present 

 many features of great interest. The Roman town appears to have 

 been crossed by streets regularly laid out, as at Wroxeter ; one 

 tessellated pavement has been found in a tolerable state of preser- 

 vation ; and there can be no doubt that, as the excavations proceed, 

 they will throw more and more light on the condition of Britain 

 under the Romans. T. W. 





PROGRESS OP INVENTION". 



Non-Explosive Gunpowder. — It has long been known that 

 filling up the interstices between the grains of gunpowder, prevents 

 or retards its explosion — room being no longer left for the expan- 

 sion of the gases which are evolved, as the grains ignite one after 

 another in rapid succession. It is not necessary that the substance 

 used to produce this effect should be non-combustible, since even 

 gunpowder itself, in a state of minute subdivision, greatly retards 

 the explosion of that which is granulated. Some materials would 

 be inadmissible as preservatives against the accidental explosion of 

 gunpowder, because they absorb moisture, others because they 

 would injure the glazing. Sand is liable to both these objections ;. 

 and most probably glass, since it must scratch the grains, and in 

 the course of time it becomes alkaline, consequently hygrometric 

 It is indispensable that any substance mixed with gunpowder to 

 protect it should be easily and thoroughly removable, though not 

 spontaneously. Now it is doubtful if any mixture of the kind 

 would remain complete during carriage ; and it may be proved, by 

 using a white powder, that a sieve would not effect a perfect separa- 

 tion — while, unless the protecting powder is completely removed 

 from the gunpowder previous to use, its goodness would be seriously 

 impaired. Mr. Gale, a chemist, of Plymouth, has recently made 

 experiments on this subject, which have attracted considerable 

 attention ; chiefly, perhaps, because it was not generally known that 

 gunpowder has long since been rendered inexplosive by means 

 identical with those used by him, but which have not been adopted 

 in practice, on account of the objections to which they are liable. 

 M. Piobert, of St. Petersburg, made experiments with inexplosive 

 powder in 1835, and M. Padeieff between 1840 and 1844. M. 

 Piobert, among the various substances which he tried, found that 

 each of the constituents of gunpowder itself would answer well ; 



