James Nasmyth: Engineer; an autobiography Part 21

At the extreme edges of the flow, where the lava had become viscid, these folds and contortions were very remarkable. They were piled fold over fold,--the result of the mighty pressure from behind.

It was sad to see so many olive gardens burnt and destroyed; the trees were as black as charcoal. It is singular to see the numbers of orange and olive growers who choose to live so near to the "fiery element." But the heat presses forward the growth of vegetation.

To be there is like living in a hothouse; and the soil is extraordinarily fertile. Hence the number of vineyards quite close to the base of Vesuvius. The cultivators endeavour to enclose their gardens with hard ma.s.ses of lava, so as to turn off the flow of the molten streams in other directions; but the lava bursts through the walls again and again, and the gardens are often utterly burnt up and ruined. Almost every field at the base of Vesuvius contains a neat little oratory, with a statue of the Virgin and Child, to which the cultivators repair in times of peril and calamity. But chapel, statue, and gardens are alike swept away by the tremendous descent of the molten lava.

As the night was growing dark, I made my way from these riskful farms to Rosina, a little village on the way back to Naples. As I had had nothing to eat or drink during this thirst-producing journey, I went into a wine shop and asked for some refreshment. The wine shop was a sort of vault, with a door like that of a coach-house, but with a bench and narrow table. The good woman brought me a great green gla.s.s bottle like a vitriol carboy! It contained more than six gallons of wine, and she left me with a big gla.s.s to satisfy my wants. The wine was the veritable Lachryma, Christi--a delightful light claret--for producing which the vineyards at the base of Vesuvius are famous.

After some most glorious swigs from this generous and jovial carboy, accompanied with some delightful fresh made bread, I felt myself up to anything. After washing down the dust that I had swallowed during the day, I settled with my liberal landlady (indeed she was mightily pleased with only tenpence), and started for Naples.

I had still an eight-mile walk before me, but that was nothing to my vigorous powers at that time. The moon had risen during my stay in the wine house, and it shone with a bright clear light. After a few miles' walking I felt a little tired, for the day's exercise had been rather toilsome. A fine carriage pa.s.sed me on the road with a most tempting platform behind. I hailed the driver, and was allowed to mount. I was soon bowling along the lava paved road, and in a short time I arrived at Naples. I made another excursion to the crater of Vesuvius before I left, as well as visits to Herculaneum and Pompeii, which exceedingly interested me. But these I need not attempt to relate. I refer my readers to Murray's Guide Book, where both are admirably described.

After completing my business affairs at Naples, and sowing the seeds of several orders, which afterwards bore substantial results, I left the city by the same line of steamers. I pa.s.sed again Civita Vecchia, Leghorn, Genoa, and Ma.r.s.eilles. On pa.s.sing through the South of France I visited the works of several of our employers, and carried back with me many orders. It was when at Creuzot that I saw the child of my brain, the steam hammer, in full and efficient work.

But this I have referred to in a previous chapter.

CHAPTER 15. Steam Hammer Pile-driver.

In 1840 I furnished Sir Edward Parry with a drawing of my steam hammer, in the hope that I might induce him to recommend its adoption in the Royal Dockyards. Sir Edward was at that time the head director of the steam marine of England. That was after the celebrity he had acquired through his Arctic voyages. I was of opinion that the hammer might prove exceedingly useful in forging anchors and large iron work in those great establishments. Sir Edward appeared to be much struck with the simplicity and probable efficiency of the invention.

But the Admiralty Board were very averse to introducing new methods of manufacturing into the dockyards. Accordingly, my interview with Sir Edward Parry, notwithstanding his good opinion, proved fruitless.

Time pa.s.sed by. I had furnished steam hammers to the princ.i.p.al foundries in England. I had sent them abroad, even to Russia.

At length it became known to the Lords of the Admiralty that a new power in forging had been introduced. This was in 1843, three years after I had submitted my design to Sir Edward Parry. The result was that my Lords appointed a deputation of intelligent officers to visit my foundry at Patricroft to see the new invention. It consisted of Captain Benison (brother of the late Speaker), and Captain Burgman, Resident Engineer at Devonport Dockyard. They were well able to understand the powerful agency of the steam hammer for marine forge work. I gave them every opportunity for observing its action.

They were much pleased, and I may add astonished, at its range, power, and docility.

Besides showing them my own steam hammer, I took the deputation to the extensive works of Messrs. Rushton and Eckersley, where they saw one of my five-ton hammer-block steam hammers in full action.

It was hammering out some wrought-iron forgings of the largest cla.s.s, as well as working upon smaller forgings. By exhibiting the wide range of power of the steam hammer, these gentlemen were entirely satisfied of its fitness for all cla.s.ses of forgings for the naval service.

They reported to the Admiralty accordingly, and in a few days we received an official letter, with an order for a steam hammer having a 50 cwt. hammer-block, together with the appropriate boiler, crane, and forge furnace, so as to equip a complete forge shop at Devonport Dockyard. This was my first order from the Government for a steam hammer.

When everything was ready, I set out for Devonport to see the hammer and the other portions of the machinery carefully erected.

In about a fortnight it was ready for its first stroke. As good luck would have it, the Lords of the Admiralty were making their annual visit of inspection to the dockyard that day. They arrived too late in the afternoon for a general inspection of the establishment; but they asked the superintending admiral if there was anything of importance which they might see before the day closed. The admiral told them that the most interesting novelty in the dockyard was the starting of Nasmyth's steam hammer. "Very well, they said, "let us go and see that".

I was there, with the two mechanics I had brought with me from Patricroft to erect the steam hammer. I took share and share alike in the work. The Lords were introduced to me, and I proceeded to show them the hammer. I pa.s.sed it through its paces. I made it break an eggsh.e.l.l in a wine-gla.s.s without injuring the gla.s.s. It was as neatly effected by the two-and-a-half ton hammer as if it had been done by an egg-spoon. Then I had a great ma.s.s of white-hot iron swung out of the furnace by a crane and placed upon the anvil block. Down came the hammer on it with ponderous blows. My Lords scattered to the extremities of the workshop, for the splashes and sparks of hot metal flew about. I went on with the hurtling blows of the hammer, and kneaded the ma.s.s of iron as if it had been clay into its devised forms.

After finishing off the forging, my Lords gathered round the hammer again, when I explained to them the rationale of its working, and the details of its construction. They were greatly interested, especially Mr. Sidney Herbert (afterwards Lord Herbert of Lea), then Secretary to the Admiralty, and Sir George c.o.c.kburn, a fine specimen of the old admiral. Indeed, all the members of the Board were more or less remarkable men. They honoured me with their careful attention, and expressed their admiration at the hammer's wonderful range of power and delicacy of touch, in this new application of the force of steam.

The afternoon was a most important one for me in more ways than one, although I cannot venture to trouble my readers with the details.

It was followed, however, by an order to supply all the Royal Dockyard forge departments with a complete equipment of steam hammers, and all the requisite accessories. These were supplied in due time, and gave in every case the highest satisfaction. The forgings were found to be greatly better, and almost absurdly cheaper than those done by the old bit by bit building-up process. The danger of flaws was entirely done away with; and, in the case of anchors, this was a consideration of life and death to the seamen, who depend for their safety upon the soundness of the forgings.

Besides my introduction to that admirable man, Mr. Sidney Herbert, I had the happiness of being introduced to Captain Brandreth, Director of Naval Works. The whole of the buildings on sh.o.r.e, including the dockyards, were under his control. One of the most important affairs that the Lords of the Admiralty had to attend to on their visit to Devonport was to conclude the contract for constructing the great docks at Keyham. This was a large extension of the Devonport Docks, intended for the accommodation of the great steamships of the Royal Navy, as well as for an increase of the graving docks and workshops for their repair. An immense portion of the sh.o.r.e of the Hamoaze had to be walled in so as to exclude the tide and enable the s.p.a.ce to be utilised for the above purposes. To effect this a vast amount of pile-driving was rendered necessary, in order to form a firm foundation for the great outer dock wall, about a mile and a quarter in length.

Messrs. Baker and Sons were the contractors for this work.

They were present at the first start of my steam hammer at Devonport.

They were, like the others, much impressed by its vast power and manageableness. They had an interview with me as to its applicability for driving piles for the immense dock, this being an important part of their contract. Happily, I had already given some attention to this application of the powers of the steam hammer. In fact, I had secured a patent for it. I had the drawings for the steam hammer pile-driving machine with me. I submitted them to Mr. Baker, and he saw its importance in a moment. "That," he 'said, "is the very thing that I want to enable me to complete my contract satisfactorily." Thousands of enormous piles had to be driven down into the deep silt of the Sh.o.r.e; and to have driven them down by the old system of pile-driving would have occupied a long time, and would also have been very expensive.

The drawings were of course submitted to Captain Brandreth.

He was delighted with my design. The steam pile-driver would be, in his opinion, the prime agent for effecting the commencement of the great work originated by himself. At first the feat of damming out such a high tide as that of the Hamoaze seemed very doubtful, because the stiff slate silt was a treacherous and difficult material to penetrate. But now, he thought, the driving would be rendered comparatively easy. With Captain Brandreth's consent the contractors ordered of me two of my steam hammer pile-drivers. They were to be capable of driving 18-inch square piles of 70 feet in length into the silt of the Hamoaze.

[Image] s.p.a.ce to be enclosed at the Hamoaze

This first order for my pile-driver was a source of great pleasure to me.

I had long contemplated this application of the power of the steam hammer. The machine had long been in full action in my "mind's eye,"

and now I was to see it in actual reality. I wrote down to my partner by that night's post informing him of the happy circ.u.mstance. The order was for two grand steam hammer pile-drivers, each with four-ton hammer-blocks.The wrought-iron guide case and the steam cylinder were to weigh in all seven tons. All this weight was to rest on the shoulders of the pile. The blows were to be about eighty in the minute. This, I thought, would prove thoroughly effective in rapidly driving the piles down into the earth.

I have said that the steam pile-driver was in my mind's eye long before I saw it in action. It is one of the most delightful results of the possession of the constructive faculty, that one can build up in the mind mechanical structures and set them to work in imagination, and observe beforehand the various details performing their respective functions, as if they were in absolute material form and action.

Unless this happy faculty exists ab initio in the brain of the mechanical engineer, he will have a hard and disappointing life before him. It is the early cultivation of the imagination which gives the right flexibility to the thinking faculties. Thus business, commerce, and mechanics are all the better for a little healthy imagination.

So soon as I had returned home, I set to work and prepared the working drawings of the steam pile-drivers. They were soon completed, conveyed to Devonport, and erected on the spot where they were to be used.

They were ready on the 3d of July 1845. Some preliminary pile-driving had been done in the usual way, in order to make a stage or elevated way for my pile-driver to travel along the s.p.a.ce where the permanent piles were to be driven. I arranged my machines so that they might travel by their own locomotive powers along the whole length of the coffer dam, and also that they should hoist up the great logs of Baltic timber which formed the Piles into their proper places before being driven.

The entire apparatus of the machine was erected on a strong timber platform, and was placed on wheels, so that it might move along the rails laid down upon the timber way. The same boiler that supplied the steam hammer part of the apparatus served to work the small steam-engine fixed to the platform for its locomotion, and also to perform the duty of rearing the next pile which had to be driven. The steam was conveyed to the hammer cylinder by the jointed pipe seen in the annexed engraving. The pipe accommodated itself to any elevation or descent of the hammer. The whole weight of the cylinder, hammer-block, and guide box, supported by the shoulders of the pile, amounting to seven tons in all, rested upon the shoulders of the pile as a "persuader;" and the eighty blows per minute of the four-ton hammer came down with tremendous energy upon the top of the pile head. No soil, that piles could penetrate, could resist such effective agencies.

[Image] Diagram of the Steam Pile-Driver

Explanation of the Diagram of the Steam Pile-Driver.--The chief feature of novelty of this pile-driving machine consists in the employment of the direct action of the Steam Hammer as the blow giving agent, and also in the manner in which the dead weight of the entire apparatus, consisting of the hammer-block C, the steam cylinder A, and its guide-case B, is employed to importantly aid the effect of the rapid and energetic blows of the steam hammer. These ponderous parts rest on the shoulders of the pile H all the while it is being driven, the pile in this respect being the only support of the apparatus A B C.

So that, besides the eighty blows per minute that the four-ton steam hammer energetically deals out to the head of the pile from a four foot fall the dead weight of the apparatus constantly acts as a most effective "predisposer" to the sinking of the pile into the ground; the hoisting chain D being let slack the while, so as to allow A B C to "follow down" the pile H, while the eighty blows per minute are incessantly showered on its head. The upward stroke of the piston, with its attached hammer-block C, is arrested at the proper height not only by allowing the steam that raised it to escape, but as soon as the piston pa.s.ses the escape holes X X, the confined air above the piston at O rebounds, and so aids most effectively in increasing the energy of the fall of the hammer-block C on the pile head.

There was a great deal of curiosity in the dockyard as to the action of the new machine. The pile-driving machine-men gave me a good-natured challenge to vie with them in driving down a pile. They adopted the old method, while I adopted the new one. The resident managers sought out two great pile logs of equal size and length--70 feet long and 18 inches square. At a given signal we started together.

I let in the steam, and the hammer at once began to work. The four-ton block showered down blows at the rate of eighty a minute; and in the course of four and a half minutes my pile was driven down to the required depth. The men working at the ordinary machine had only begun to drive. It took them upwards of twelve hours to complete the driving of their pile!

Such a saving of time in the performance of similar work--by steam versus manual labour--had never before been witnessed.

The energetic action of the steam hammer, sitting on the shoulders of the pile high up aloft, and following it suddenly down, the rapidly hammered blows keeping time with the flashing out of "the waste steam at the end of each stroke, was indeed a remarkable sight. When my pile was driven, the hammer-block and guide case were speedily re-hoisted by the small engine that did all the labouring and locomotive work of the machine; the steam hammer portion of which was then lowered on to the shoulders of the next pile in succession. Again it set to work.

At this the spectators crowding about in boats, p.r.o.nounced their approval in the usual British style of "three cheers!"

My new pile-driver was thus acknowledged as another triumphant proof of the power of steam.

The whole of the piles for this great work were speedily driven in.

The wall was constructed, and the docks were completed in an unusually short time. The success of my pile-driver was followed by numerous orders. It was used for driving the immense piles required for the High Level Bridge at Newcastle, the great Border Bridge at Berwick-upon-tweed, the Docks at Tynemouth, the Docks at Birkenhead, the Docks at Grimsby, the new Westminster Bridge, the great bridge at Kief in Russia, the bridge at Petersburg, the forts at Cronstadt, the Embarrage of the Nile, at Yokohama in j.a.pan, and at other places.

It enabled a solid foundation to be laid for the enormous superstructures erected over them, and thus contributed to the permanence of many important undertakings.

The mechanical principles on which the efficiency of the steam pile-driver chiefly depends are as simple as I believe they are entirely novel and original. The shoulder of the pile acts as the sole supporter of the ponderous ma.s.s of the hammer-block, cylinder, and guide-box. This heavy weight acts as a predisposing agency to force the pile down, while the momentum given by the repeated fall of the hammer, at eighty blows the minute, brings the constant dead weight into full action. I am not aware of any other machine in which such a combination of mechanical forces is employed.

Another very effective detail consisted in employing the waste steam in the upper part of the cylinder for the purpose of acting as a buffer to resist any undue length of the upward stroke of the piston.

But for this the cylinder covers might have been knocked off.

The elastic buffer of waste steam also acted as a help to the downward blow of the hammer-block. The simplicity and effectiveness of these arrangements form--if I may be allowed to say so--a happy ill.u.s.tration of my "Definition of Engineering," the application of common sense in the use of materials.

The folding-up steam pipe with which the steam was conveyed from the boiler to the cylinder at all heights, and the way in which the folding joints accommodated themselves to the varying height of the cylinder, was another of my happy thoughts. In fact, this invention, like most others, was the result of a succession of happy thoughts.

The machine in its entirety was the result of a number of common-sense contrivances, such as I generally delight in. At all events, this most effective and novel machine was a special favourite with me.

I may mention, before concluding this branch of my subject, that pile-driving had before been conducted on what I might term the artillery or cannon-ball principle. A small ma.s.s of iron was drawn slowly up, and suddenly let down on the head of the pile at a high velocity. This was destructive, not impulsive action. Sometimes the pile was shivered into splinters, without driving it into the soil; in many cases the head of the pile was shattered into matches, and this in spite of a hoop of iron about it to keep the layers of wood together. Yet the whole was soon beat into a sort of brush.

Indeed, a great portion of the men's time was consumed in "reheading"

the piles. On the contrary, I employed great ma.s.s and moderate velocity. The fall of the steam hammer-block was only three or four feet, but it went on at eighty blows the minute, and the soil into which the pile was driven never had time to grip or thrust it up-- an impediment well known to ordinary pile-drivers. At the end of the driving by my steam hammer, the top of the pile was always found neat and smooth, indeed more so than when the driving began.

I may again revert to my interview with the Lords of the Admiralty on the occasion of my first meeting them at Devonport. I was residing at the hotel where they usually took up their quarters while making their annual visitation of the dockyard. I was honoured with an invitation to confer with Sir George c.o.c.kburn, Mr. Sidney Herbert, and Captain Brandreth on a subject of considerable importance; namely, the proving of chain cables and anchors required for the Royal Navy. The question was mooted as to whether or not some permanent injury was done to both by the test strains to which they were submitted before being put on board ship. This was a subject of vital importance. The members of the Board requested me to act as one of a committee to inquire into the subject. I felt much gratified by the invitation and gladly accepted it.

On discussing the subject with these gentlemen that evening, I found that Sir George c.o.c.kburn entertained an ingenious theory in support of his apprehensions as the effect of "over-proof" straining of cables and anchors. It was that they were originally in the condition of a strong man who had to lift some heavy weight, requiring him to exert his muscular strength to the utmost; and, although he might perform the feat, it was at the cost of a permanent injury, and that he might never be able to lift the same weight again. This, however true it might be with regard to flesh and bone structures, was scarcely true with respect to mechanical agencies. I proposed a simple experiment with chain cables, which, it occurred to me, would show quite a different result--namely, that the capability of resisting the severest proof-strain would rise rather than fall at each successive proof of the same chain cable.

To test the correctness of my supposition, we had a first-cla.s.s chain cable put into the proof machine,and subjected it to such a strain as to break it again and again, until at last it was divided almost into single links. As I expected, the proof or breaking strain kept rising and rising as each successive remaining portion of the cable was torn asunder, thus showing that no injury to the natural tenacity of the chain had resulted from the increased proofs to which it had been subjected, and that the last broken links had been much more resisting than the first. The same cla.s.s of demonstrative experiments was made with anchors, and other wrought-iron work used in the service.

The Admiralty officers were much gratified with the result, as removing a groundless but very natural apprehension, heightened, no doubt, by the suggestions that had been made to the Admiralty, that their standard proof strain was not only too high in itself, but produced permanent damage to what at the outset was of the toughest iron.

My system of continued proof-straining was, in fact, another exemplification of the "Survival of the Fittest"!

A very interesting truth came out in the course of our experiments.

It was that the chief cause of failure in the links of chain cables arose, not so much from their want of tenacity, or from the quality of the iron, but from some defective welding in the making of the links.

To get at this truth, many excellent cables as received from the contractors, as well as veteran ones that had held great ships riding at anchor in terrible gales, were pulled asunder link by link by an intentional destructive strain by the proving machine.