4th April 1863) by compressed air instead of steam. I call your attention to this, as you may contradict, if you think proper, the assertion in the article above mentioned, that the idea originated with Bartlett."

I did not, however, contradict the assertion. I am glad that my description and drawings proved in any way useful towards the completion of that magnificent work, the seven-mile tunnel under Mont Cenis.

Chilled Cast-iron Shot.

In like manner, I proposed the use of Chilled Cast-Iron Shot at a meeting of the Mechanical Science Section of the British Association, held at Cambridge in October 1862. Up to that time hardened steel shot had been used to penetrate thick iron plates, but the cost was excessive, about £30 a ton. I proposed that Chilled Cast-Iron should be substituted; it was more simple and inexpensive. Considerable discussion took place on the subject; and Sir William Fairbairn, who was President of the Section, said that "he would have experiments made, and he hoped that before the next meeting of the Association, the matter would be proved experimentally. A brief report of the discussion is given in the Times of the 7th October, and in the Athenaeum of the 18th October, 1862. Before, however, the matter could be put to the test of experiment, Major Palliser had taken out his Patent for the invention of Chilled Cast-Iron Shot, in May 1863, for which he was afterwards handsomely rewarded.

I do not wish to "grasp" at any man's inventions, but it is right to claim my own, and to state the facts. The discussion above mentioned took place upon a paper read by J. Aston, Esq., Q.C., who thus refers to the subject in his letter to me, dated the 7th January 1867:

"I perfectly remember the discussion which took place at the meeting of the British Association at Cambridge in 1862, upon the material proper to be used as projectiles. The discussion arose after a paper had been read by me in the Mechanical Section upon 'Rifled guns and projectiles adapted for attacking armour plates.' The paper was, I think, printed by the Association in their Report for 1862. You spoke, I believe, at some length on the occasion; and I recollect that you surprised and much interested all who were present, by strenuously urging the use of Chilled Cast-iron for shot and shell, intended for penetrating armour plates.

"Having embraced all opportunities, and I had many at that time, of ascertaining all that was done in the way of improving rifled projectiles, I entertained a very strong opinion that experiments had shown that ordinary cast-iron was, as compared with steel, of very little value for shot and shell to be used against iron plates. For that reason, I remember I took an opportunity, after the termination of the discussion, in which you held your own against all comers in favour of chilled cast-iron, of questioning you closely on the subject, and you gave me, I admitted, good reason for the opinion you expressed. You also urged me to cause a trial to be made of chilled cast-iron for shell, such as I had shown to the section, and which (in hardened steel shot) had been fired by Mr. Whitworth through thick iron plates. This I had not an opportunity of doing. Term began soon after, and Temple occupations then took up all my time. "There can be no doubt whatever that any one who may claim to have been before you in teaching the public the use of Chilled Cast Iron for projectiles intended to penetrate iron plates, must give proof of having so done prior to your vigorous advocacy of that material at the Cambridge Meeting in 1862. -- Yours very sincerely, "J.Aston."

In another letter Mr. Aston says -- "It is quite right of you to assert your claim to that which in fact belongs to you." I did not, however, assert my claim; and, with these observations and extracts, I leave the matter, stating again the fact that my public communication of the invention was made in October 1862; and that the patent for the invention was taken out by Major Palliser in May 1863.

Mr Nasmyth's final comments on his inventions and contrivances.