Mr. White's Design for the New Lotidon Bridge. 333 



between the two axes 6, where is always to be <180°, 

 and next designate the angle which this plane forms with the 

 plane of xi/ by 0, and tlie angle of the same plane with the 

 plane of x'y by *, both so taken as to be the interior angles 

 of a spherical triangle, we shall have 



7K = COS ^ e sin i (*■ + *) = I V'M 



n = COS I & cos i (* + 0) = -^ -/N 



p = sin ^ e cos ^ (*^— cp) = i ^p 



q = sin i e sin | ('/>— 0) = j ^Q 



And thence we obtain the values of all other angles, in which 



the situation of Y and Y', the prolongations of the positive i/ 



andy, depend on the side of the plane passing through x and 



.r', on which the angles have been taken, and in which also the 



points Z and 7i', which are in the prolongations of the positive 



z and z', fall on the contrary side of the plane of xt/ to that 



on which X' is situated. 



XLVI. Papers relating to a Desig7i for the Neto London 

 Bridge, 07i the Principle of Cementitious Architecture : — ex- 

 hibited to the Committee of the House of Commons, on the 

 1 Ith of April ] 823. By John White, Esq. 

 [Concluded from page 270.] 

 VIII. On Calcareotis Cemeiits. 



To the Editor of the Quarterly Journal*. 

 Sir, 

 TJTAVING for nearly thirty years experienced practically 

 -*•-'■ the imperfections of the various cements in use in Eng- 

 land, I have been led into a variety of examinations of them, 

 and do not hesitate to communicate to you (as a portion of 

 the papers on my design for New London Bridge), an account 

 of a series of experiments which will, in my opinion, con- 

 tribute essentially to a knowledge of the subject. 



The first endeavour at investigation was made by a com- 

 parison of various burnt clays obtained in the neighbourhood 

 of London and in Kent, with the imported pozzolano, as sold 

 in London : but the imj)orted material was so variable in its 

 nature, that little resulted beyond a knowledge that it pos- 

 sessed more calcareous matter, and that it was more uncertain 

 and variable in the sizes of the grains, than that of British 

 manufacture. 



The next endeavour was to ascertain what practically were 

 the best sizes of the particles to be used with lime, and in what 



• We were not aware, when these papers were communicated to us by 

 the author, nor indeed until tliey had been made uj) for tlie prcbcnt Nuin- 

 hcr, lliat tills section '' {)ii ndcnrcnus rcinrula'''' had alrcaily a|)pcarcd in the 

 (jtuarterly Journal ollScifntf) vol. xx. p. .)0.— Kdii. 



State 



