Chain Suspension Roofs. 275 



tlieir character, their direction, their force, their co-ordination, 

 and it dies, and then physical and chemical actions, with the 

 co-operation of the minute organisms which the microscope 

 reveals, pull the fabric to pieces, imparting new motions to its 

 molecules, and as soon as they are dispersed, other forces im- 

 parting motion take them in their grasp, arranging them 

 in fresh patterns, causing them to enter in new combinations, 

 again to be destroyed by other motions, reconstructed again, 

 and thus " On, on, for ever." 



CHAIN SUSPENSION KOOFS. 



BY SIR JOHN HEESCHEL, BAKT., K.H., ETC., ETC. 

 (With facsimile of the Original Sketch.) 

 We have much pleasure in publishing the following interesting 

 letter from Sir John Herschel, and in presenting to our readers 

 a lithographed facsimile of the original rough sketch embodying 

 his design. 



The principle of this mode of construction will be readily 

 intelligible to engineers ; but for the benefit of those who are 

 not accustomed to rough diagrams, we may state that the 

 sketch represents (the front wall being removed) a per- 

 spective view of the interior of a great hall. A light iron 

 roof, of double convex form, and internally strengthened by 

 angular supports, is kept in its place by chains, attached to it, 

 and passing over the side walls of the apartment, which act 

 like the piers of a suspension bridge. This we take to be the 

 plan of M. Lehaire, and if so, it will be seen that Sir John 

 Herschel had anticipated him by thirty years. 



To the Editor of the Intexxectttal Observes. 



Collingwood, October 3, 1865. 



Sir, — In your number for September I observe the following 

 notice under your miscellaneous heading, " Roofs on the Principle 

 of Suspension Bridges." " M. Lehaire, a French civil engineer, pro- 

 poses to construct roofs having a span very far greater than hitherto 

 attempted by supporting them with suspension cables. They will 

 have an advantage over suspension bridges in being free from the 

 injurious effect produced by varying loads." 



Allow me, in the absence of any further knowledge of M. 

 Lehaire's suggestion, to submit for your inspection (and if you think 

 propei% for that of your readers, through the medium of a woodcut) 

 the exact facsimile of a rude sketch of a plan for constructing a 

 hall 600 feet in length, 400 in breadth, and 200 in height, which I 

 find preserved among my papers, and which, if the date it bears be 

 (as I have no doubt it is) that of its execution, assigns nearly 

 thirty years for the lapse of time. The handwriting is the same 

 with that of the other memoranda on the paper, and the discolora- 



