307 
place. I referred to the lever only, as one common-sense mode of illus- 
trating the effect of the removal of the hoop further from the axis, on 
the assumption that the tub or gun burst by opening at one side only, 
and turning round the opposite one at the internal surface, both parallel 
to the axis. This, however, is at present immaterial. 
At the date of this, my first visit to Dr. Hart, my designs for the 
36-inch mortars, as actually contracted for, and substantially as finally 
carried out, had been completed. They were made throughout with- 
out either assistance or help of any sort from Dr, Hart or any one else, 
as I am sure he is ready to testify, so far as he is concerned. I leave 
the Academy to form its own opinion of Captain Blakely’s renewed at- 
tempt, in his paper read here on the 28th of May last, to make it 
appear by an extract from Dr. Hart’s letter in ‘‘ The Mechanic’s Maga- 
zine” (February 21, 1857, p. 176), and otherwise, that Dr. Hart was in 
fact the real designer of those mortars, and ‘‘ that he, and not Mr. Mallet, 
was an original and independent inventor.” This suggestion was first 
broached in December, 1857, through ‘‘The Press’ London news- 
paper, and, though then formally refuted by me in that paper and 
in ‘The Mechanic’s Magazine,” has been again produced by Captain 
Blakely. I trust Dr. Hart is here to give this his own contradiction, 
once for all. 
That for which I was, and have always acknowledged myself, in- 
debted to Dr. Hart was his mathematical investigation of the precise 
amount of increase of strength producible by annular construction with 
initial tension, and of the law regulating the theoretically exact propor- 
tioning of the superimposed tensions. His investigation was communi- 
eated to me in a letter dated the 6th of July, 1855, and in one of expla- 
natory detail afew days later, andis contained in the Note W to section 
282 of my paper ‘‘ On the Physical Conditions involved in the Construe- 
tion of Artillery,” read to this Academy on the 25th of June, 1855. 
The equation (4) for solid made guns, i.e., guns made on the old or 
common plan (given at section 274 of the text of my paper as Dr. 
Hart’s), was communicated to me by him on the 17th of May, 1855. 
It was the only communication I had from Dr. Hart previous to the 
reading of my paper to this Academy; it has nothing to do with the 
matter before us; and I only allude to it as accounting for Dr. Hart’s 
name thus appearing in the ¢ew¢ of my paper read on the 25th of June, 
1855; while his investigation, contained in the Note W, and referring to 
the question now before us, was not, as I have stated, communicated to 
me until the 6th of July, 1855. The notes to my paper were added as 
the text was passing through the press, and it is so stated in the preface 
to the separate issue of the paper, published without alteration from the 
Transactions of the Academy. 
Dr. Hart’s investigation enabled me to know the precise tension at 
which each ring should be shrunk on upon the 36-inch mortars then in 
progress, and gave exactitude to my previous general notions on ringed 
construction; but I saw that the method he proposed for regulating 
this, viz., by difference of temperature only, could not be practically car- 
