termination of the curve or that next the centre; the curve is such that it produces an easy cleaving action in the water. By this form of the advance edges of the blades a further advantage results, which is this, that any spars, rope, or wreck with which the screw blades may come in contact are thrown off in a radial direction, or have a tendency to be so acted on; the propeller therefore assists to clear or effectually clears itself from any wreck or material with which it is liable to come in contact. By forming the advance edges as described, as they enter and leave the opening in the dead wood of the ship, the transition is gradual, and therefore will not induce shakes or tremulous motion, so perceptible in all vessels propelled by screws by reason of the right line edges thereof striking the disturbed water throughout their whole length, and the violent reactions of such water in propelling, the water in the dead wood being in a comparatively quiescent state and inoperative as regards propulsion. I also form these advance edges of the blades of screw propellers of steel or other suitable metal so sharpened or serrated like a saw that they will sever any unyielding obstacle with which they may come in contact in the manner of a circular saw."

Mr. Griffiths' letter to the Times determined Sir Howard to vindicate his claim, and he took counsel of his friend Lord Lyndhurst, who recommended him to submit the facts to Mr. Carpmael, of Southampton Buildings, and he obtained from that authority the following opinion:

"I have very carefully examined into the claim made by General Sir Howard Douglas, in regard to

his being the first to devise the screw propeller-blade of the particular form shown and described at page 61 of his work on Naval Warfare with Steam.' This propeller-blade consists in a modification of the Admiralty screw propeller, each blade of which was formerly made of about one-sixth of a helix or complete screw, with the forward or leading edge, and also the after edge, perpendicular to the shaft; consequently such a blade increased in width the further it proceeded from the axis, and was widest at its outermost edge or periphery.

"Sir Howard Douglas, as I understand his claim, alters this propeller-blade in respect to its leading or forward edge only, and he does so by removing parts of such forward edge, so that, in place of its being a straight line, he makes it into a convex curved line, and he leaves the after edge of the blade as heretofore.

"If the above be the correct expression of Sir Howard Douglas's claim, I am clearly of opinion that he was the first to devise and publish that particular form of screw propeller; and I am further of opinion that, whatever be the advantages which may arise from the use of that propeller-blade, to Sir Howard Douglas will be due the merit of having originated it.

"I am intimately acquainted with Mr. Griffiths' screw propeller-blades, and I can only imagine that that gentleman, when he wrote the letter to the Times newspaper on the 30th August last, was uninformed of the precise nature of Sir Howard Douglas's claim, or he would not have fallen into the error of supposing that Sir Howard Douglas claimed his (Mr. Griffiths') previous invention. It is of the

essence of Mr. Griffiths' invention, and of his patent, that screw propeller-blades should become 'narrower or tapered towards their outside extremities, in contradistinction to the form hitherto adopted of increasing the width of that part of the blade. Now, Sir Howard Douglas's propeller-blade does go on increasing in width as it proceeds outwards from the axis, and it is widest at the periphery, consequently his blade is the reverse of that invented by Mr. Griffiths.

"I would further state that the giving a convex curved form to the forward or leading edge of a screw propeller was not new either to Sir Howard Douglas or to Mr. Griffiths, Lowe and others having used and published descriptions of screw propeller-blades with curved forward or leading edges; but these propellers differed in other respects both from those of Mr. Griffiths and also from those of Sir Howard Douglas. "WILLIAM CARPMAEL.

"24, Southampton Buildings, 27th September, 1859."

This opinion satisfied Sir Howard, and he communicated it to Mr. Griffiths, who could not impeach its fairness. Indeed, he admitted that he had "nothing to complain of in Mr. Carpmael's opinion," but maintained that he was acquainted with the advantages of the curved blade years before, though he had not made it available. Such assertions carry no weight, and Sir Howard has established the right of any one to use his propeller without interference from Mr. Griffiths. "You may with the most perfect propriety

1 Letter from Mr. Griffiths to Sir Howard Douglas, in the 'Douglas Papers.'

go on making and maintaining your claim to the particular form of screw propeller as if you had received no letter from Mr. Griffiths," writes Mr. Carpmael to Sir Howard, in reference to this letter. "He cannot take any proceedings at law against you for so doing." Yet the nation continues to pay a royalty for Mr. Griffiths' propeller, when it has here a better one without charge.'

6

1 Messrs. Maudslay altered their opinion of the Douglas principle on witnessing the trials of the Ariadne,' the results of which they communicated to Sir Howard. These showed an increase of speed in his form of blade, though not to a great extent, but were decisive in the correction of the vibration which causes the deflection in steerage, and is such a strain on the ship:-"The Ariadne' having been originally built for engines of greater power, the screw aperture was one foot larger fore and aft than in any of the other vessels fitted with engines of the same power, which was much in favour of less agitation, and the stern was not nearly so much shaken by the action of the propeller as in other vessels; and to this we may add that on the last trial, when the forward corners were cut off, it was agreed by all that it was still more reduced; in fact, that THERE WAS NO AGITATION PERCEPTIBLE. We have the honour to be, &c., MAUDSLAY, SONS, and FIELD."

CHAPTER XXXIX.

PRONOUNCES AGAINST ARMOUR SHIPS.

THE great interest Sir Howard took in naval gunnery led him to consider whether ships might increase their means of defence, as well as their powers of attack; and he was prepared to decide the question when Sir Robert Peel consulted him as to the expediency of building iron vessels of war in 1848. He declared that iron ships would not be invulnerable, and recommended Government to forego the pursuit of an impossibility, and turn its attention to the development of artillery, which might be carried to an indefinite extent, and given irresistible penetration. His arguments prevailed, and the notion was dropped for a time, but revived as a movement when the Emperor Napoleon launched the 'Gloire,' the public being brought to believe that squadrons could be as effectively protected by armour as the knights of old, who fought battle after battle without drawing blood. Sir Howard showed the fallacy of this view, but conceded that we must take up the armour to the same extent as the French. "Although we would not have initiated such a system," he observes, "yet so long as our neighbours the French persist in building iron-cased ships, we must do so likewise, and that in a manner to keep well ahead of anything the French or any other power may do for aggressive purposes. I think, therefore, the country is much indebted to Sir