1842.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



287 



that after receiving about 50 blows 

 over tlie edge of the anvil, it 

 passed into the form given in fig. 5, 

 the fracture being entirely Jibrmis, 

 like wood, of a fine lead gray colour, 

 and totally free from the appearance of 

 any sparkling crystals. This experi- 

 ment, then, warrants the conclusion, 

 that the appearance of the fracture is 

 also no criterion of the quality of the 

 iron, if temperature be left out of the 

 question, inasmuch as 40^ has not only 

 vastly improved the tenacity, but also 

 wrought an entire change on the aspect 

 of the grain of the iron. It is well 

 known to practical men that a very few 

 degrees of heat will most materially 

 affect not only the appearance of the fracture of iron, but also its tenacity. 

 But for my reluctance to occupy more of the space of your excellent 

 journal, I should most gladly have given farther details and experi- 

 ments ;* but I trust such as I have endeavoured to describe will be in 

 some degree acceptable, and be productive of useful results. I would 

 most strongly recommend all who are interested in such matters, and 

 who have the opportunity, to repeat the experiments themselves,'!' as 

 I doubt not the results would not only agree with what I have found 

 and stated, but also tend to rivet the recollection of them in their 

 minds, as the subject is one of the very highest importance to all, 

 especially to those whose professional character and success may be 

 influenced by possession or otherwise of such plain workshop facts. 



I have no desire to make any great claim of discovery here, but I 

 shall feel highly gratified, if what I have brought to light as to the 

 vast accession of shock-resisting quality conferred on wrought iron hy 

 the combined action of cold hammering and subsequent annealing should 

 prove, as I am confident it will, a substantial benefit to all who have either 

 their lives or property depending on pieces of /Brought iron, whether in 

 the case of a railway axle, or other application. 



I am no advocate for over-burdening the attention of engineers 

 with compulsory clauses in specifications, but I would most strongly 

 recommend attention to annealing of all bolts and axles, on which 

 much depends. The recommended process requires no extra expense 

 or trouble worth naming, and companies would do well to see that 

 such was attended to. 



Bridgewater Foundry, I am, Sir, 



near Manchester, Yours most respectfully, 



Aug. 1, 1842. James Nasmyth. 



NOTES ON STEAM NAVIGATION. 



Engine Frames. — The foot or projection descending from the 

 diagonal stay to the condenser or main centre bracket is, in our 

 opinion, superfluous and inexpedient. If the attachments of the 

 main centre to the bottom are such as they ought to be, this projection 

 from the diagonal stay can have no upward pressure thrown upon it ; 

 and if the bottom attachments are insufficient, the diagonal stay is unable 

 to resist the upward pressure without injurious straining and vibra- 

 tion. The attachment for the main centre is best, we consider, when 

 cast in the form of a bracket on the sole plate, as in the engines of 

 the Trent and Isis, by Messrs. Miller and Ravenhill. The bottom 

 part of the engines of Messrs. Maudslays and Co. consists of too many 

 pieces : the sole plate is one casting, the condenser another, and the 

 main centre bracket a third ; and these parts have to be fixed together 

 by bolts, and there is a joint of great superficies between the sole 



' We sincerely hope that Mr. Nasmyth will not hesitate to favour us with 

 all the information he can upon so important a subject, and we feel assured 

 that we are only echoing the sentiments of our readers in expressing such 

 a desire. — Ecitok. 



T And record them in tlie Journal. — Editor. 



plate and condenser, which is undeniably a very bad thing. In Messrs. 

 Miller's engines all these parts are cast together: the sole plate, con- 

 denser, and main centre brackets consist of only one piece which is 

 certainly much the best system. 



All the bolts in the framing for the purpose of connecting the several 

 parts of it together should be turned with a little taper, and the holes 

 should all be widened out. If this be not done, the framing will be 

 very likely to work. Where there is much side strain upon the bolts 

 they should be of steel. The soles of the plummet blocks and the places 

 they rest on upon tlie frame should be planed all over ; the outsides 

 of the paddle shaft brasses, and the insides of the plummer blocks 

 should also be planed all over ; fitting strips will work into the sub- 

 stance of the brass, and the bearings will get slack sideways without 

 the possibility of tightening them. Horns to the crank beams are 

 unnecessary, if the framing be well fitted and bolted, but if adopted, 

 should have some means of being tightened sideways as well as fore 

 and aft, in the sockets on the beams in which the horns slide. A hori- 

 zontal cross between the engines is a very useful attachment; and the 

 connecting pieces at the end of the engines between the frames should 

 extend upwards and downwards on the columns, so as to obtain as firm 

 a hold of them as possible. The surfaces should all be planed, and 

 the holes widened. A common planing machine maybe made to plane 

 sole plates, cylinder faces, or framing by fixing a bracket to carry the 

 tool upon the carriage, and bringing the thing to be planed to the side 

 of the machine, and there fixing it. A string attached to a ratchet 

 operating on a screw may be easily made to move down or forward the 

 cutter. 



f'alve and parallel motions. — The valve motion of one engine is 

 identical with the piston motion of the other engine; and the parallel 

 motion shaft of the one engine, by being extended to the other engine, 

 might be used to work that engine's valve. A combination, too, of 

 the motions of the two engines might be used to work the expansion 

 valve, so that both the slide valves and expansion valves might be 

 worked without either cams or eccentrics. To carry this out in 

 practice it would be necessary to have a solid shaft within a hollow 

 shaft, extending from engine to engine, the parallel motion of the one 

 engine being connected with the solid shaft and the parallel motion of 

 the other with the hollow shaft. The parallel motion, then, of the 

 starboard engine would work the larboard valve, and vice versa. The 

 expansion valve might be a slide valve working on the inner flat 

 surface of an ordinary short D, with the upper tails connected so as 

 to form a port, and wrought by a spindle through a hollow valve rod. 

 The motion proper to the expansion valve might be obtained from 

 the combined or antagonistic motions of the solid and hollow shafts, 

 which sometimes move in different directions, and at other times in 

 the same. 



The best sort of foot and discharge valves would be the slide valve, 

 and indeed the valves of the several pumps might also be made slide 

 valves, with much advantage. The slide valve vfill neither make a 

 noise, nor get gagged with chips or dirt. By way of parenthesis, we 

 may remark that the slide valve seems to be peculiarly well adapted 

 for the feed-pumps of locomotives. If the air pump were furnished 

 with a slide instead of flap valves, it might be made double-acting, 

 and with half the size would maintain a better vacuum in the con- 

 denser than is attainable by the existing modes. There would then, 

 of course, be no valves in the bucket, which would become, in fact, a 

 common piston. It would be easy to work the injection slide by the 

 engine, so as to apportion the quantity of water to the quantity of 

 steam— a measure of each being admitted every stroke— and to make 

 the rate of its admission more nearly identical with that of the flow 

 of steam into the condenser. This would probably have the effect of 

 making the vacuum steadier, and would prevent the engines from 

 being choked with water when brought up in a sea way, if used in 

 conjunction with a cataract. 



The most convenient way of packing slide valves is from the back. 

 The packing screws should come through a cross bar supported by 

 proper lugs in the casing, so as to take the strain off the door, and 

 should then extend through brass bushes rivetted into the door, and 



2 R 2 



