J 844.] 



THE CIVIL ENGINEER AND ARCHITECT'S JOURNAL. 



4& 



from it that tTie doorway is a circular arch springing from two co- 

 lumns, and above it there appears to be a kind of pointed arch also 

 placed on two columns; whereas these, as also eight of the other 

 openings at their sides, have segmental and triangular pediments with 

 the centre of the horizontal cornice broken away. This breaking 

 away of the cornice forms a principal feature in the erection called 

 York stairs, London, and of which Mr. Gwilt favours us with a view 

 and the following eulogium, page 207, " York stairs, another of his 

 (Inigo Jones) examples, exhibits apurenessand propriety of character 

 which appear afterwards unappreciated by his successors, with Wren 

 at their head." Alas, Sir Christopher, is it come to this? and from a 

 Palladian— £< tu, Brute. But although our Encyclopffidist is severe, he 

 is not consistent, for at page 745 he tells us "that no pediment should 

 be tolerated composed otherwise than of two raking unbroken and 

 one horizontal unbroken cornice." 



The description of the Duomo, which accompanies the plate, is not 

 very lucid, at least to a "mere amateur;" he says, "In the third 

 story from the bottom" (very precise) "a painted" (?) "window, 

 separated by three rauUions, is introduced. The rest" (?) " of the 

 facade is vertically divided by buttresses into five parts, &c." 



I have given one example of unsophisticated contradiction. We 

 shall now have another of a different complexion, made with so much 

 caution, so much acumen and foresight, that it would almost appear 

 he had provided for the enjoyment of the literary sin, and at the 

 same time secured a retreat in case of an indictment being framed 

 against it. The safety valve shall here be given in italics : — page 57, 

 "In all imitations of that" (Greek) "style, its" (arch) "introduction 

 produces discord which no skill can render agreeable to the educated 

 eye. Attempts have been made by the modern German archi- 

 tects to introduce the use of the arch with Greek forms ; but they 

 have been all signal failures, and that because it is incapable of amal- 

 gamation with the solemn majesty and purity of Greek composi- 

 tion. Be/ore such blending can be accomplisTied wilh success, 

 the nature of pure Greek architecture must be changed." Now 

 the whole of this was written as a kick at the German school, 

 ■which he never omits giving when opportunity serves — but to the 

 contradiction, page 718, "an arcade or series of arches is perhaps 

 one of the most beautiful objects attached to the buildings of a city 

 which architecture alTords." No doubt can be entertained of the 

 nature of these arcades, which when not in German hands find so 

 much favour in Mr. Gwilt's eyes; they are neither arcades without 

 columns nor yet Gothic compositions, but the pseudo Greek arcades, 

 of which he gives a number of examples from Vignola, Palladio and 

 Chambers. No doubt our author will say that the style is successfully 

 changed by the Italians but not by the Germans before the addition of 

 the arches. On one occasion an eminent architect, knowing I was 

 only a "mere amateur," kindly offered to show me a Greek dome of 

 Lis own designing: of course he knew better, but he did not think 

 that I did ; however, on ray expressing a doubt of the Greeks having 

 known anything about domes, his reply, though not so terse, was tan- 

 tamount to what Mr. Gwilt might give on the present occasion. 

 " Nous avous change tout cela." 



It would be too german to our author's antipathies not to admit 

 that his work has some merit, and that in 1053 pages the reader may 

 find much information, which can only be gleaned from a more ex- 

 tended surface elsewhere. The ground plan (if we may so speak) is 

 well arranged, and has the advantage of some ground plans in leaving 

 plenty of room for improvement in the filling up. The application 

 of a highly condensing power to literary effusions, except in the actual 

 process of elim.ination, is bad ; it ought to be applied to the ore in the 

 author's head, and not to the metal in the printer's form. The type is 

 too small for continuous reading, and three volumes might be given to 

 the binder instead of one. And this arrangement would be of advantage 

 to the " mere amateur," as the principal part of the second book on 

 mathematics can be learned more fully elsewhere. 



Having concluded, at least for the present, the notice on the 

 Encyclopsedia, which is given with all the modesty and hesitation of 

 a first appearance in the character of a reviewer, the writer feels 

 called on to say a few words in defence of giving his name to what 

 he writes. That it may be well in most cases for writers in the mis- 

 cellaneous periodical press of the day, to write anonymously, is rea- 

 dily conceded ; but no necessity calls for it in a respectable profes- 

 sional journal, where all who contribute should have but one object 

 in view — the advancement of science. A name, although (as in the 

 present instance) it may have no intrinsic merit attached to it, yet 

 encourages some to read and others to write. 



LORD EOSSE'S TELESCOPE. 



At a meeting of the Belfast Natural History Society, the steps by which 

 difficulties were overcome in making the speculum, were explained by Mr. 

 Stevelly in detail, under the following heads : — 



Metal for thk Speculum. — The metallic alloy for the speculum con- 

 sists of four atoms or chemical combining proportionals of copper to one of 

 tin, or by weight 126'4 copper to 58-9 tin. This alloy, which is a true che- 

 mical compound, is of a brilliant white lustre, has a specific gravity of 8'Sll ; 

 a twelfth of a cubic foot, or 114 cubic inches of it, weighing, therefore, a little 

 over 45}Ib. avoirdupois, or to allow for all waste when casting, 001b., which is 

 the rule by which Lord Rosse estimates the weight of metal he requires. 

 This alloy is nearly as bard as steel, and yet is almost as brittle as sealing 

 wax. Of this most unpromising material Lord Rosse has cast, ground, and 

 has ready for polishing, a circular mass G ft. in diameter, o^ inches thick, and 

 weighing upwards of three tons, with a surface perfectly free from crack or 

 flaw, and quite homogeneous. The next head is 



Casting. — On the first castings having flown into pieces, finding that the 

 fragments no longer fitted each other in their former places, he peiceived 

 that they bad been in a state of violent strain arising from the cooling and 

 setting of the outer parts, while the inner parts, yet fluirl, were also largely 

 expanded by the heat ; this, and the porous surface, led him by many stages 

 and trials to the remedy, which is simple and complete. The bottom of the 

 mould is made of a ring of bar iron, packed full of slips of iron hoops set on 

 their edges, which lie in parallpl chords of the ring. These, though packed 

 very tightly together, and so closely fitting that the melted metal cannot nm 

 between them, yet allow any air that is carried down to the bottom of the 

 mould when the metal is cast in, to pass out through the interstices. After 

 the ring is packed, it is secured in a lathe, and the face, which is to be the 

 bottom of the mould, turned true to the convex shape to fit the concave 

 speculum required. It is then placed flat on the ground by spirit levels (be- 

 tween the furnace in which the metal is melted, and the anneaUng oven), and 

 the mould completed at the side with sand, in the way practised by founders, 

 but left open at top. The metal is then melted in cast iron crucibles ; 

 wrought iron would be corroded by the speculum metal, and injure its pro- 

 perties, while fire clay crucibles will not answer. Unless the crucihles he cast 

 with their bottoms downward, they will be porous, and the melted alloy will 

 run through their fine pores. When the metal is melted, and still much too 

 hot to pour, the crucibles arc brought by a crane, and set firmly, each in. a 

 strong hoop iron cradle, which turns on gudgeons, and so arranged round the 

 mould that when the handles of the cradles are depressed, they pour out 

 their molten mass direct into the mould. An oxide forms rapidly on the 

 surface of the metal while too hot — this is as rapidly reduced back to the 

 metallic state by constantly stirring t with a pine rod ; as the temperature 

 sinks, the instant this reduction of the oxide begins to cease, is seized on as 

 the proper moment for pouring. The liquid mass descends with a few fiery 

 splashes, and after waving back and forward for a few seconds, the surface 

 becomes still. The setting process begins at the hoop-iron bottom, where a 

 thin film first sets — the process extends upwards in horizontal layer i and at 

 length the top, though red, becomes fixed in form ; the mass is then as 

 tough as melting glass, and being turned out of tlie mould upon a proper 

 truck, with the face upwards, is drawn into the oven to undergo the pro- 

 cess of 



Annealing, or very slow cooling. Here it is built up into the oven, pre- 

 viously heated red-hot, and fire is kept up under the floor of the oven for 

 some days; the under fire-places are then stopped, and all left for weeks to 

 cool down to the temperature of the air. The six feet speculum was left here 

 sixteen weeks. Here the particles of the alloy slowly arrange themselves 

 into the arrangement in which the aggregating forces are in equiUbrium, or 

 natural and equal antagonist tension. When the oven is opened, the speculum 

 is removed to the workshop, to undergo the process of 



Grinbing, which process was illustrated by working a raodeh In the 

 workshop it is placed on a circular table, in a cistern filled with water, of 

 temperature, say 55° Fahrenheit, with the face to be ground upwards. The 

 circular table is turned round by the motion of the grinding-engine. But 

 first, the edge is made tiuly cylindrical by being surrounded by many pieces 

 of deal board set in an iron ring pressing against the edge ; emery being in- 

 troduced as it turns round, soon grinds it cylindrical; it is then placed in the 

 box in which it is to he used ; here it is firmly secured by a ring of iron 

 brought to embrace, firmly yet gently, its now truly cyUndrical edge. The 

 box and speculum, with the face to be ground placed upwards, is now again 

 placed on the circular table in the cistern of water. Emery and water being 

 placed upon it, the grinding disk is laid on, which is a cast iron plate turned 

 at one surface to the shape to fit the speculum when ground, and grooved on 

 that surface with many annular grooves concentric with the plate, aud with 

 many straight grooves running across at right angles to each other. The 

 hack of this grinding plate is ribbed with six or eight radial ribs, to give it 

 stiffness. This plate sits rather loosely in a ring of iron a httle larger ia 

 diameter, which is driven back and forward by the motion of the steam-engine. 

 This ring has two motions, longitudinal and transverse. The engine causes it 

 to make 'H-h strokes for one turn of the speculum on its axis under the grind- 

 ing disk, about 80 strokes taking place in a minute ; the length of this stroke 

 is one-third of the diameter of the speculum. The motion is produced by an 

 eccentric pin. The transverse stroke takes place 1-72 times for each turn of 

 the speculum, and its extent is, at the centre of the speculum, -ms ^i ^'^^ 



