214 Report on the Progress and State of Ajjplied Mechanics. 



is based on experimental data, in some cases of great intricacy and 

 obscui-ity, of which our knowledge is in many respects imperfect, and 

 which are in the course of being augmented every day. 



32. The principles of stability, especially as regards masonry, were 

 well understood by the Eomaus and by the Mediseval architects. The 

 beauty of architecture depends, to a great extent, upon their observance. 

 Amongst the contributions that have of late been made to our know- 

 ledge of them, may be mentioned the researches of Mr. Moseley, on the 

 Stability of Structures ; and those of Mr. Yvon-Villarceaux, on the 

 Stability of the Arch (published in the Menioires des Savants Etrangers, 

 vol. xii). The latter paper contains the first complete mathematical 

 investigation of the conditions of equilibrium of an arch, under fluid 

 pressure, which are also those of many arches, under a solid pressure ; 

 and the manner in which the solution is obtained by means of eUiptic 

 functions, is such as must inspu-e every mathematician with admiration. 

 The results, when appUed to practice, are likely to conduce materially 

 to the stability, economy, and beauty of large stone bridges. The 

 theory of the stability and pressure of earth has recently been reduced 

 to a system based on the sole law of the proportionality of the friction 

 to the pressure, without any of the " mathematical artifices" hitherto 

 employed ; and a principle, called that " of the transformation of struc- 

 tures,''' by means of which, when a structure possessing stability has 

 been designed, the figures of an indefinite number of other structures, 

 also possessing stability, can be deduced from it by projection, may be 

 expected to prove of some utility. 



33. A mere catalogue of the names of those who have contributed, 

 by their labours, to our knowledge either of the mathematical theory 

 of the STEEN&TH 01" MATERIALS, or of its experimental data, would 

 occupy a considerable time m being read. Yom- Eeporters, mentioning 

 only those who at present occur to their remembrance, have to name 

 Galdeo, Leibnitz, Huyghens, Hooke, Boyle, Newton, the Bernouillis, 

 Euler, Boscovich, Coulomb, Belidor, Vince, Dupin, Marriotte, Smeaton, 

 Robison, Musschenbroek, Young, Kennie, Bevan, Tredgold, Eondelet, 

 Telford, Brewster, Fresnel, Gauss, Savart, Chladni, Navier, Poisson, 

 Oersted, CoUadon, Sturm, Mossotti, Cauchy, Lam6, Clapeyron, Grassi, 

 Regnault, Wertheim, Chevandier, CariUion, Kirwan, St. Venant, Ponce- 

 let, Yvon-ViUarceaux, Morin, Green, Stokes, M'Cullagh, Haughton, 

 Kelland, Dunlop, Fincham, Mushet, Pasley, Brown, Brunei, Hodgkm- 

 son, Fairbairn, Stephenson, Clark, P. Barlow, P. W. Barlow, W. H. 

 Barlow, Couch, Smith, Dobson, Galton, James, Daniell, Wheatstone, 

 Watson, Kupfer, Forbes, Gordon, William Thomson, James Thomson, 

 Jellett, Maxwell, Mallet, Russell, Fowkc, Mendis. 



