1843.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL 



3S!» 



years since, had three close Umber hulk-hcails, intended for Hie same purpose 

 as the iron ones. 



Mr. Williams replied that they would not answer the same purpose as the 

 iron ones, and that if a vessel had only three hulk-heads, making four com- 

 partments, if one of them was broken into, the vessel would sink, hut with 

 five compartments it would he saved. With regard to the general durability 

 of iron vessels, he recollected an iron vessel being built at the llorseley iron- 

 works more than 20 years since, which be believed was still in existence ; 

 and a small boat, built for him by Mr. Grantham, of very thiu plates in the 

 year 182-1, was still at work. 



The Secretary stated that the vessel alluded to by Mr. Williams, was the 

 Aaron Manby, which was built by, and named after his father in the year 

 1821. It was the first iron vessel that ever went to sea ; it had been very 

 roughly used, and the engines and boilers bad been more than once renewed ; 

 yet the hull bad scarcely required any repairs, and it was very slightly cor- 

 roded, although it had been severely tried by being used in both fresh and 

 salt water upon the river Seine, for which service it was built. 4 It was well 

 known in Staffordshire, that many iron canal boats which were used indis- 

 criminately for carrying coals, iron ore, limestone and other cargoes, and 

 had received scarcely ordinary attention, were upwards of 40 years old, and 

 were still serviceable. ° 



Mr. Braithwaite said that he had recently heard of the sale of a wooden 

 vessel 15 years old, which was still sea-worthy, and was capable of being 

 insured. 



The President observed, that although part of two evenings had been de- 

 voted to Mr. Mallet's paper, yet that such was its value, that it could scarcely 

 be discussed until members could pursue it at leisure, and enter into the 

 wide field of observation which it embraced : it was a paper of undoubted 

 merit, and the attention of the Publication Committee had been directed to 

 it by the Council, in order to its general circulation, with the former valuable 

 paper, by the same author, as soon as was practicable. 



Electro-Magnetic Telegraphs. 



A pair of electro-magnetic signal telegraphs, constructed for the Aix-la- 

 Chapelle railway, from the plans of Professor Wheatstone, were exhibited. 



Professor Wheatstone explained, that the principle of this signal telegraph, 

 which he considered to he the most efficient arrangement for practical pur- 

 poses, was the same as his last electro-magnetic telegraph, in which a dial, 

 or hand, was caused to advance by the alternate attractions and cessations of 

 attraction of an electro-magnet, occasioned by corresponding alternate com- 

 pletions and interruptions of the circuit, by means of a peculiarly con- 

 structed apparatus, placed at the opposite end of the telegraphic line. The 

 present signal telegraph was intended for the use of the inclined plane on 

 the railway at Aix-la-Chapelle, where only a limited number of signals were 

 required ; the entire alphabet of the complete telegraph, was therefore dis- 

 pensed with, and the instrument was restricted to six elementary signals. 

 The letters M, s, c, t, b, &c, on the face of the dials were the initials of the 

 German words for engine, rope, train, telegraph, &c. The dial was eight 

 inches in diameter, and the characters were conspicuous, so that they might 

 be readily seen at a distance ; the hand, which was required to be made very 

 light, and to keep its form, was of blackened mica. The cross being re- 

 served to indicate the quiescent condition of the apparatus, there remained 

 five available characters, which, combined two and two, gave 25 signals— a 

 number amply sufficient for the purposes of the railway. It being esta- 

 blished as an invariable rule, that each signal should consist of two charac- 

 ters followed by the cross ; were the telegraph to act in any way irregularly, 

 the index would, at the end, point to some other character, instead of the 

 cross, and this would indicate that the preceding signals were wrong, so that 

 if the signals received, should not correspond with those sent (which, how- 

 ever, could not be the case if ordinary care was taken), no mistake could 

 possibly arise, because they carried with them the evidence of their error. 

 The instruments were furnished with a simple means of bringing the hand 

 immediately to the resting point, without interfering with the circuit. As it 

 might be occasionally required to transmit a permanent signal, which should 

 remain, until a person arrived to inspect it, the five simple characters could 

 be employed for this purpose. 



■' '• Iron as a Material for Ship-building," by J. Grantham, Svo., London, 

 1 £.42. p. ti. 



5 In a letter from Mr. John Laird, dated June 29, 1843, he says, respecting 

 the probability of corrosion in iron vessels, " I beg to state that the following 

 vessels have iiad their boilers replaced (some of them twice), and that the 

 bottom and sides of the vessels near the boilers have been found quite free 

 From corrosion ; in fact, the paint originally put on was almost perfect: — 



Lady Lansdowne, built in 1833 



Garry Owen 1834 



ElizaPrice 1836 



Duncmnon 18,'iti 



Duchess of Lancaster 18311 



" The En pinnies steamer, built in 1834, has had her machinery taken out, 

 and been converted into an accommodation boat for passengers for the Indus. 

 The hull of the vessel was found quite perfect, free from corrosion, and as 

 perfect and sound as the day she was launched."— Sec. Inst. C. r.. 



The instruments at each station consisted of a telegraph, an alarm, and a 

 communicator; they would be arranged in the circuit, in several ways to suit 

 particular purposes, but no other alteration was requisite to ell'ect this, than 

 a change in the disposition of the terminal wires, and of their connexions 

 with the communicators. The telegraphs might be so placed, that they 

 would act simultaneously, when either of the communicators was worked, 

 or they might be so arranged that the instrument at one station, should only 

 be acted upon by the communication at the other, which, in many cases, was 

 preferable, as a great resistance was thereby taken out of the circuit. Other 

 arrangements, useful under particular circumstances, were also practicable. 

 This telegraph, even when all the letters of the alphabet were employed, 

 required only a single circuit of communications between the two stations. 

 Professor Wheatstone's former permutating magnetic needle telegraph, 

 though possessing a power of combination far exceeding that of any pre- 

 ceding telegraph, in which magnetic needles were proposed to be employed, 

 required a number of wires proportionate to the number of signals. 



By employing the earth, or an extent of water, to return the current, or 

 complete the circuit — which might he done, by connecting the two extremi- 

 ties of one of the communicating wires with plates of metal, and plunging 

 them into the earth or into water — one of the communicating wires might 

 be entirely dispensed with ; this plan would be adopted at Aix-la-Chapelle. 

 That a large extent of earth, or a portion of a river, could be made to com- 

 plete an electric circuit, was long since established with respect to electricity 

 of high tension, by the extensive experiments of Dr. Watson, in 1748, and 

 others ; and the same thing was proved with regard to voltaic electricity, by 

 the independent experiments of Erinan, Basse, and Aldini, made in 1803. 

 Enqan's experiments were performed in the river Havel, near Potsdam ; 

 those of Basse in the river Weser, and the environs of Hamel ; and Aldini's 

 researches were prosecuted on the shore near Calais. Professor Steinheil 

 also employed the earth as a means of completing the circuit, in the electro- 

 magnetic telegraph which he established at Munich in 1838. 



A pair of Professor Wheatstone's telegraphs were established at Berlin in 

 the beginning of 1812 : the line of communication was a single wire, carried 

 through the air upon wooden posts, and plates of metal attached to the ends 

 of the wire were buried in the ground. In the same year he formed a com- 

 munication between King's College and the shot tower on the opposite side 

 of the river: the communicating wire was laid along the parapets of Somer- 

 set-house and Waterloo-bridge, and thence to the top of the tower, where 

 one of the telegraphs was placed ; the wire then descended, and a plate of 

 zinc attached to its extremity was plunged into the mud of the river; a si- 

 milar plate was attached to the extremity at the north side, and was im- 

 mersed in the water. The circuit was thus completed by the entire breadth 

 of the Thames, and the telegraphs acted as well as if the circuit was entirely 

 metallic. The peculiar construction of the present signal telegraph, enabled 

 a magneto-electric machine to be substituted for a voltaic battery. This 

 source of electric action not being subject to cessation or diminution, the 

 attention necessary for keeping a voltaic battery in order, was dispensed 

 with, and the instruments were always ready for action, without any previous 

 preparation. 



ON ITIESCO PAINTING. 



Abridgment of Mr. Charles II. Wilson's Report to the Com- 

 missioners of the Fine Arts. ' 



Mr. Wilson in this report first describes and considers the construction of 

 the walls on which frescos and other mural paintings are executed, and then 

 proceeds in order with the other portions of his subject. 



Mural paintings were executed upon plaster of various kinds, laid upon 

 walls variously constructed ; several examples also occur of frescos which 

 were painted upon plaster laid on lathing. The comparative durability of 

 works executed under these circumstances Mr. Wilson explains by several 

 examples, on the Continent. They are found on three kinds of wall : — 

 ashlar walls of Gothic edifices — brick walls of buildings of different dates — 

 and upon coarsely built rubble walls of different kinds. To these are to he 

 added frescos on lath, of which there are many examples in different parts 

 of Italy. From the observations which have been made by Mr. Wilson, it 

 appears that plaster will not stand well upon ashlar walls, unless the stones 

 he small and the seams open ; for if the plaster he loosened from this kind 

 of wall by damp or accident, it entirely falls away in large masses, showing 

 that it does not adhere firmly to the masonry. Brick walls are the best for 

 fresco, and the practice of the careful Germans and modern Italians are in 

 favour of this opinion. 



There are many specimens of frescos upon lath in Italy ; the most ancient 

 is that of the "Trionfo della Morte," by Orgagna, in the Campo Santo of 

 Pisa. The artist probably adopted the precaution from having entertained 



1 C. H. Wilson, Esq., Director of the Government School ol Design :>t 

 Somerset House, was, in the course of the last year, employed by Her Ma- 

 jesty 's < 'ommissioners on the Fine Arts to proceed to the Continent to collect 

 information relating tu the objects of the Commission. Having been fur- 

 nished wiih the necessary instructions be left England in August and re- 

 lumed in January last. 



