CONSTRUCTION OF THE BUILDING.

71

tion by poles acting as supports to them. Two other girders being then hoisted, and Axed,and slipped between the connecting-pieces on the remaining two sides of thesquare, a perfect table was constructed. The “ shores ” or supports were thenremoved, together with the shear-legs, and the whole apparatus was at liberty, forthe purpose of recommencing a similar operation in an adjoining 24-feet bay.

When a sufficient number of these bays had been completed, starting from the The second andintersection of the nave and transept, to warrant the addition, the hoisting of the mencing withoutcolumns for the first floor was commenced ; more lofty shear-legs being of courseemployed. The extension of the ground-floor structure proceeding as that of thefirst floor was carried on, a base was in turn afforded for the columns of the thirdtier; and thus the iron framework of the whole building rose from the ground,firm and secure, without involving the necessity of any scaffolding whatever.

While these operations of actual structure were being carried on, under the The preparationimmediate superintendence of Mr. John Cochrane, the work of preparation ofaieother " ork 'was yet more vigorously pushed. The manufacture of the Paxton gutters, andthe application of machinery to their formation, is so interesting as to warranta somewhat lengthened notice.

In the year 1837, when Mr. Paxton commenced the construction of the The gutter-Chatsworth Conservatory, in which similar gutters were employed, machinery m ' lkmstnaclime:had not been brought to bear upon their construction. By the use of a con-trivance, the details of which were arranged by Mr. Cowper, a gentleman inthe employment of Messrs. Fox and PIenderson, a total length of upwards of2,000 feet per day has been turned out, for many successive days. The piecesof timber destined to form the gutters are sawn into lengths of 24 feet, 6 inchesdeep and 5 inches thick. Three of these pieces are fixed on the frame of aplaning-machine, and by it are worked true and square. In figures 19, 20, 21,and 22 are given representations of the details of the gutter-making machine,erected at Messrs. Fox and Henderson’s workshops, near tire Thames, at Chelsea.

Fig. 19 is a side view of a block of cast-iron, to whichsteel cutters (AAAA) are attached by bolts and nuts(BBBB). Four blocks, of similar construction, arefixed to four spindles, and by the action of drums onthe same spindles, set in motion by bands moved by asteam-engine of 20-horse power, the blocks are madeto revolve with extreme rapidity. Any piece oftimber exposed to the action of these cutters, mustobviously be scooped out into the form of the outlineof the cutters attached to each block. By modifying

the form of the cutters, almost any variety of section can be given to the timbersbrought into contact with them. In the present case, the four sections A, B, C,and D (fig. 21), represent the successive action of the four sets of cutters letteredto correspond with them (on fig. 20), by means of which the larger cavity for therain water, and the two smaller channels for the condensed water, are formed.

The part removed by each set of cutters is shown by the hatched lines.

Fig. 22 represents a plan of the machine, looking down from above upon thegutters, the gutter being removed in order to show the action of the cutters moreclearly.

The operation may be explained as follows :—The piece of timber, properly its ™«ie «fsquared, is placed upon the roller marked E ; it is then pushed on until it comes pera ° n

Fig. 19.

U R