THE ROYAL ARTILLERY INSTITUTION. 
215 
very imperfect. It had, in fact, hardly any attachment. A superficial longi¬ 
tudinal mark now shewing in the chamber on both sides, about 16 ins. long 
and *05 in. in greatest depth, he regarded as the last trace of one of those 
transverse fissures referred to at p. 209, which are apt to occur in the heart 
of all large forgings. Much difficulty, he remarked, had been experienced in 
obtaining sound forgings for the centre piece of the mortar chambers, and in 
every forging a rent extending more or less across a diameter in the axial plane, 
was found to exist when the forging was bored into. The gibs and cotters 
had been, he said, intentionally reduced in strength to a minimum, that they 
might spring a little, and so ease the jar of recoil upon the holding-down 
bolts; but this had been carried a little too far. He attributed the bending 
of the rear retaining screw to the misfit of the quoins, which had warped 
and shrunk in the many months that had elapsed since they were fitted, and 
only bore at one end, being free about 0*3 in. at the other. 
Fig. 3. 
Lower outer ring ply. 2nd segment of cliase. 
Examination made on 26th October, 1857, after firing of the 19th October, and mortar taken 
asunder. 
15. The mortar was repaired, at a cost of £56, in about two months, 
and the practice was resumed on the 18th December, when two medium 
and four heavy shells were fired, with a charge of 40 lbs. (Table II.) After 
the sixth discharge it was found that the centre hoop of the exterior ply of 
the bottom ring of the chase was broken through. This hoop was 3*9 ins. 
thick and 8*75 ins. wide. The joint between the bottom and centre ring 
was a good deal opened, to a maximum width of 0T25 in., and filled with 
hard fouling. A few more superficial marks had appeared, but in other 
respects the mortar was uninjured. 
29 
