Notices respecting Neto Books. 53 



In Section I. Art. 6, an important Table, as to the savino- 

 of calculation it effects, is now added, to show the load or 

 pressure in hundred-weights, while a cylindrical Pillar, Co- 

 lumn or Post of Cast Iron (without enlarged ends, or an at- 

 tached Base or Cap) will sustain with safety, when of any of 

 the several given diameters from 1 inch to 12, and lengths 

 from 2 to 24- feet of Column. Art. 8 a contains the descrip- 

 tion of this third Table ; and two practical Examples for ex- 

 plaining its use, will be found in Art. 19 b . In a Note in page 

 9, Mr. Thomas Farnolls Pritchard, a Shropshire Architect, 

 who died in October 1777, is stated to have been the pro- 

 poser and designer, in 1773, of the Jirst Cast Iron Bridge 

 which was anywhere erected, viz. over theSevern near Brose- 

 ley and Colebrook-dale, and that Mr. A. Darby, to whom 

 (by the Society of Arts) this merit has been assigned, merely, 

 as a speculator, furnished part of the Money for carrying 

 Mr. Pritchard's design into execution, under the superin* 

 tendence of a Mr. Daniel Onions, in 1777. 



In Section II, in Art. 15 is described, a new and very sim- 

 ple and durable Weighing Machine^ for Waggons, Carts, &c. 

 not exceeding 4 Tons : it is founded on the direct propor- 

 tionate flexure and return, of a Cast Iron Beam (or two such) 

 16 feet long, 7 inches broad, 5 inches deep in the middle 

 and 2^ at its ends, where it is supported. The descent of 

 the middle point, with a 4 Ton load, would be 1*7 inch: 

 which, when multiplied 5 times by a Lever, would cause an 

 Index to move, one-tenth of an inch for each Cwt. of load. 

 Art. 19 a explains the use of Table II, in the case of a Load 

 uniformly distributed over the length of a Beam (like that of 

 the weight itself of a heavy Beam) and directs, half of this 

 load to be considered, as acting on the middle point of the 

 Beam, when supported at its ends : In a future Edition it may, 

 for the satisfaction of the practical Man, be well, to explain 

 here in words, why half the uniformly distributed load, is to 

 be used in applying Table II, and why five-eighths of such a 

 load is to be used, in applying Table I, Arts. 18 and 19. In 

 this Section, the number of popular Examines is much in- 

 creased. 



In Section IV, Art. 34 b Mr. Tredgold explains a new 

 principle of constructing Cast-iron Bridges, which would not 

 be affected by contraction and expansion, such as has im- 

 paired several of our finest constructions of this kind : a large 

 Bridge on this construction, might be put together in parts, 

 and erected without the assistance of centering. 



In Section V. Arts 59 b to 59 h , the Author's latest Expe- 

 riments are detailed, on 12 Specimens, of 6 different kinds of 



Cast 



