392 Progress in Science. (July, 
tracing the history of the introduction of rifling cannon in this country, the 
author then gave the results of certain competitive trials which took place in 
1863, and after describing the simplicity of the Scott centreing iron-bearing 
projectile, and the peculiarities of its construction, it was observed that the 
distribution of strain and the perfect centreing in the bore fully accounted for 
the grooves of the Scott gun having been as perfect at the end of the compe- 
tition as when the gun left the factory. It also explained why the centreing 
shot of the same weight, fired with similar charges, escaped out of its gun so 
much more readily than the French or Woolwich one, striking a far more 
heavy blow. The relative merits of the uniform and increasing spiral were 
then dwelt upon, and the superiority of the former system most conclusively 
proved by reference to the results of actual experiment. It was shown that 
the stud system of centreing was ill-adapted for any rapid twist of spiral, and 
it was stated that the question of long-bearing centreing projectiles versus the 
short-bearing non-centreing system was now under consideration. 
Torpedos.—A very interesting paper was recently read by Mr. C. W. Merri- 
field, F.R.S., before the Institute of Naval Architects, on ‘‘ Torpedo Warfare,” 
the main consideration being as to how a vessel may best be constructed with 
a view to defending it from the aétion of torpedos: the one great principle 
advocated by Mr. Merrifield being that of sub-division. Extending armour 
plates over the bottom of a vessel, whilst it would add considerably to its dis- 
placement, would not afford any sure means of defence; for approaching a 
coast known to be protected by torpedos, a number of small ironclads were 
preferable to one large one, as in the event of a serious accident the loss in life 
as well asin material would be less. Again, these vessels should be absolutely 
subdivided into compartments, with air-tight coverings, so that in the event 
of an accident to one compartment, the water might be driven out by means 
of pumping air into it. In order to neutralise the effect of the blow given by 
the explosion of a torpedo, the author proposes that the bottoms of 
vessels should be constructed with double cells, the lower one being filled with 
water, which, acting as a buffer, would distribute the blow of concussion and 
render it less injurious to the fabric of the vessel; the upper cells should be 
connected by means of pipes and stop-cocks with an air-pump, so that in the 
event of the middle skin becoming broken the upper cell would be cleared of 
water by means of a ‘‘ plenum.” 
Sewage of Paris—Our neighbours across the Channel, no less than our- 
selves, are engaged in the consideration of that most important of all sanitary 
questions, viz., how best to dispose of town sewage. The Paris sewers at 
present discharge themselves into the Seine at Clichy and St. Denis, by two 
principal outfalls, giving a daily discharge of 8,850,000 cubic feet, which affects 
the water of that river in three different ways. The sand and mud are depo- 
sited near the outfall of the two collectors, and the volume of the deposits 
reach the amount of 3} millions of cubic feet a year; they produce fermenta- 
tion in the warm weather, and it is necessary to dredge constantly at a yearly 
cost of about £8000. The light mud and organic matters rest on the surface 
of the river and pollute the water for a considerable distance, and the soluble 
matters produce serious impurities. Since 1867 experiments have been going 
on, first at Clichy, and subsequently at Grenvilliers, for the purification of 
the sewage waters with sulphate of alumina, and for utilising them for 
fertilising purposes. The Conseil des Ponts et Chaussées now, after recom- 
mending a complete dredging of the Seine, state that the experiments made at 
Grenvilliers having given satisfactory results as to the disinfecting the sewage 
water by their application to irrigation, and by their purification with sulphate 
of alumina, and these results being such that, if they were known to have a 
durable efficacy, they would prevent the discharge into the Seine of the impure 
sewage water, they counsel the Municipal Administration to continue and 
to develop these experiments. The Prefect has now submitted for the appro- 
bation of the Municipal Council a proje& which will, however, only deal with 
less than a third of the Paris sewers, but will form a part of the complete 
scheme. Should the work be undertaken we hope to be able to give further 
particulars regarding it it in a future number. 
