84 



THE CIVIL ENGINEER AND ARCHITECrS JOURNAL. 



[March, 



ing on Iwo boats, so tliat when the bridge is required to be opened, both 

 boats are willidrann, one towards each shore. The Willem lock is 297 

 feet 8 iucli'^s long, 51 feet !i inches wide; the height of the lock walls being 

 32 feet iuchcs, and the gates being each 20 feet 5 inches by 29 feet 4 

 inches. 



The iolal cost amounted to one million and a half pounds sterling. The 

 time required by vessels to make the passage from Amsterdam to the Hel- 

 der varies according to their size, and the means of haulage ; fly-boats, 

 wiih six relay of four horses each, making it in ten hours, whilst large 

 i".;ist Indiamen require two, three, and four days, according to the wind. 

 The (Iclails of construction of the whole of the works were given 

 very freely and with illustrated drawings. In the discussion which 

 ensned, it wiis staled that the only canal in this country which could be con- 

 trasted witli that of the Helder, was the Caledonian canal, which was 

 projected iipou a report by Watt, commenced by Jessop, and in a great 

 part constructed by Telford, a few years previously to the Helder canal. 

 The principal dillcrence between the two consisted in the nature of the 

 ground ihroush which they were cut, the former being excavated entirely 

 out of alluvial deposit, whilst the latter had to be cut out of hard gravtl, 

 and in some cases rock. An interesting account was given of the mode of 

 forming the spot for the entrance-lock at the Inverness end of the Caledo- 

 nian canal. The object was to carry the work out into deep water. A 

 large mass of earth was deposited in the sea to the full extent intended. 

 Upon this mound, a heavy load of material was laid to consolidate the 

 mass. After settling for a considerable time, the upper mass was removed, 

 the excavation was made fur the lock-pit, and the construction was ef- 

 fected with com|iarative facility, and had endured much rough weather 

 since, vviiliout any symptoms of failure. The superincumbent vieight 

 which was removed, being greater than any subsequent strain, there was 

 no danger of the lock ever smking. 



On the ICilh inst., this paper was continued, and treated principally of 

 the art of building with fascine work, as practised in Holland and 

 {;ermany. 



The usual construction of these dykes was described to be, by sinking 

 .-successive layers or beds of fascines or faggots of almost 30 inches thick by 

 from 8 to IG jards in width, and of proportionate length, weighted with 

 gravel and stones mingled with clay, sea-weed, and silt. These layers 

 were couliaued until they reached above the sea level, when the top was 

 coEStructeil of more solid materials, and sometimes capped with brickwork, 

 as the public roads were formed upon them. 



The slopes of the faces of the dj kcs vary considerably : some of the low 

 dykes are in section of the form of an arc of a circle of to 10 feet chord 

 and 10 inches to 1 foot versed sine, covered with fascine matting, staked 

 down upon a clay-bed. Others have a base of 19 feet wide and 5 feet of 

 a triangular section, also nisde up of fascines Jaud stakes, secured by 

 hurdles i<nd wattling, with clay, peat, sea-shells, and sand, well rammed 

 in, and then co^ered with turf. Others are formed with rows of piles, IG 

 feet long, with their heads G or 7 feet above the shore, joined longitudinally 

 and laterally l>y waling timber, filled in and arouud with fascine beds and 

 weishieil with stone. Baskets tilled with sand are also used in certain 

 silua! 03S, as well as various modihcatious of all ihese kinds of protection.s. 

 It was stated that these constructions were found to succeed better and 

 last as long as stone, being at the same time about half the cost. 



ON GUNPOWDER. 



Dr. Faiaday, in a lecture delivered at the Royal Institution, gave some 

 account of the " Compositio7i and Qualities of Gunpowder" — its composi- 

 tion contains 75 parts of nitre, 15 parts of charcoal, and 10 parts of sul- 

 phur; which, converted into equivalents, give 1 of potassium,! of nitro- 

 gen, 6 of oxygen, S'4 of carbon, and O'bS of sulphur, in a state of mecha- 

 nical mixture. 



The Aciiun of Gunpowder. — Gunpowder is a solid body, in which a 

 source of enormous power is locked up, capable of being brought into 

 immediate operation whenever wanted : the action thus elicited being 

 itself regulated by human skill with wonderful precision. 1 he enormous 

 quantity of gas generated by the combustion of gunpowder, irrespective 

 of heat, was exhibited. It was remarked that, on the ignition of gun- 

 powder, though the sulphur begins the combustion, it is not itself burned 

 by the ox J gen of the nitre, but unites chiefly with the potassium of that 

 salt to form sulphuret of potassium, a substance which assists in giving to 

 the flame of gunpowder an intense heat. If gunpowder and steel lilings 

 be dropped together through four or five inches of flame, the latter will 

 burn, tliougli the former will not. A Dame from gas was made to play for 

 several seconds on a heap of gunpowder, without lighting it ; but when 

 actually lighted, it evolves very great heat. It is to the immense heat 

 produced on t!ie solid products of the combustion of gunpowder, that the 

 certainty of its complete combustion is greatly owing. In this respect 

 gunpowder differs characteristically from gun-cotton. The latter fires at 

 a heat which would not allect the former; but produces, by its combus- 

 tion a degree and condition of heat much less communicable to other 

 bodies. 'J he ellcct of the (beat generated, independent of the chemical 

 «hauge from the solid to the gaseous or vaporous state, was illustrated by 



the violence with which a mixture of one volume of oxygen with two of 

 hydrogen gas bursts the vessel which contains it, solely in consequence of 

 the heat el'cited during their combination. This is manifest from the fact 

 that the space occupied by the uncombined gases is greater by one-half 

 than that taken by the resulting steam. 



Granulatiun. — Prof. Faraday laid great stress on the effect of the gra- 

 nulation of gunpowder. To this condition of gunpowder, presenting, as 

 it does, a number of separated surfaces of size just sufiicicnt to become 

 surrounded with flame at the same instant of ignition, much of the disrup- 

 tive or projectile ellect of gunpowder was ascribed. It was shown that, 

 without thai porosity which its division into grains imparls to a mass of 

 gunpowder, the explosion of the nhole could not be instant nor simulta- 

 neous. This was proved by bringing a piece of mill-cake successively 

 into the condition of grain powder and of meal powder. The slow com- 

 bustion of the solid meal powder fuse was compared with tlie quicker in- 

 flammation of the hollow rocket and the instant inflammation of the charge 

 of a gun. All these effects are related to the condition of the interior of 

 the gunpowder in respect of its permeability by the flame of the fir.st par- 

 ticles ignited. Then, as to its exterior condition, it was shown that the 

 tardy burning of the miner's fuse is due to the granular state of the pow- 

 der in its case being counteracted by the pressure of the strands of rope 

 wrapped very tightly round it ; while, on the other hand, in the cracker of 

 the firework-maker, a similar train is instanily fired throughout, because it 

 lias a loose jacket all over it, and, in the burning of the common cracker, 

 an alternation of these efleots is produced. 



The great importance of Time in producing the effects of Gunpowder. — 

 Contrasting the action of gunpowder with that of fulminating mercury and 

 silver, or of those still more fearfully explosive compounds, the chlorides 

 of nitrogen and of iodine, Prof. Faraday showed, that, if the explosion 

 of gunpowder were really instantaneous, it would be useless for all its 

 present applications. As it is, however, whenever gunpowder is fired in 

 the chamber of a gun, it does not arrive at the full intensity of its action 

 until the space it occupies has been enlarged by that through which the 

 ball has been propelled during the first moment of ignition. Its expansive 

 force is thus brought down and kept below that which the breach of the 

 gun can bear, whilst an accumulaiing, safe, and eflicieot momentum is 

 communicated to the ball, producing ihe precise efl'ects of gunnery. This 

 manageable action was contrasted witli the efl'ect of a morsel of iodide of 

 nitrogen put on a plate, and exploded by being touched by the extremity 

 of a long slick. The parts immediately in contact with the iodide were 

 shattered, — i. e., the end of the slick was shivered, and the spot in the 

 plate, covered by that substance, was drilled as if a bullet were fired 

 through it, yet no tendency to lift the stick was felt by the hand ; whereas 

 the comparatively gradual action of gunpowder lifts and projects those 

 weaker substances, wadding and shot, which give way before it. 



ORNAMENTAL GLASS. 



Mr. Apsley Pellatt delivered a lecture at the Royal Institution on Feb. 

 12, " On the manufacture of ornamental glass." He explained that the re- 

 fractive pellucid colourless brilliancy of flint-glass was owing to the pre- 

 sence of lead ; and that fliut glass, or more properly glass of lead, most re- 

 sembled rock crystal or the diamond ; and in this branch of the trade, espe- 

 cially as regarded table and chandelier glass, the British glass-manufac- 

 turers were pre-eminent, and superior to their continental rivals. The en- 

 tire manipulalion in the making of a wine-glass, jug, barometer-tube draw- 

 ing, patent pillar moulded vase, were explained in detail both from large 

 diagrams and from the practical exhibition of these processes by two work- 

 nii n : a furnace having been fitted up by Mr. Pellatt in the theatre of the 

 Inslilution for the express oliject ; also salt-cellars were pressed by ma- 

 chinery, bottles blown and moulded, spun-glass drawn, &c. During these 

 operations Mr. Pellatt explained the conditions of whetting oflT by the ap- 

 plication of ihe sudden contraction of the cold iron tools, so that a slight 

 blow would separate the bowl of a wine-glass from the glass adhering to 

 the blower's crow ; that a punty might be applied to the reverse end for 

 shearing and linishing the bowl. 'Ihe punty is a solid iron cane, with a 

 little hot glass adheriug to it for handling glass pieces ; which, by partial 

 melting of the glass in the course of manufacture, is again removed by a 

 tap when it is no longer required. The peculiarity of glass welding by 

 coutact (impossible if the slightest film of sulphur intervene), and various 

 manipulations, were detailed, parlii ularly ihe projecting moulded pillars 

 which possessed the refractiie and brilliant eflect of cut glass; and although 

 invented and intro<luced a few years since by Mr. Jan.es Green as a no- 

 velty, it was found, ou comparison with a Roman specimen of glass dug 

 up lu the city of London, the properly of Mr. Roach Smith, apparently to 

 have been manufactured by means ofthe same appliances as the ancients, 

 the fragments having a perfectly even interior, with a projecting pillared 

 exterior. 



The difference of glass made by hand and in moulds was stated by the 

 lecturer, as well as the distinction between moulded blow-offs with cut 

 scolloped edges, v^hich were far superior in the interior polish, as con- 

 trasted with articles, such as dishes and salt-cellars, pressed in moulds by 

 mechanical power, as introduced by the American system, whose interior 



