184 1.] 



THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. 



291 



quainted with the subject knows that the number of courses being odd 

 or even has nothing at all to do with the meeting of the joints. 



Next, (referring to the same page), about dividing the line E A, 

 fig. 1, we will here take a iigure with his own letters as example, 

 Suppose it was required to construct an oblique arch of the following 

 dimensions, viz. : 



Span 10 feet = A C. 

 Rise 2-5 feet. 



Angle of obliquity 45° = A H C. 

 Width of bridge IG feet = A u. 



And take the case he does at page 7, in supposing the number of 

 courses to be nine; following out the directions given by him, namely, 

 to draw F K to meet the straight line A E perpendicularly in K, E K will 

 be divided into eight courses, and A K will be the ninth ; nhich mould 

 require eight counes to be 1/oot 10'17 inches thick, and the remaiiwig one 

 to he G'3G inches thick. Now I would ask, does Mr. Nicholson really 

 come forward with such a rule as this, and call his book a Guide to 

 Raiheay Masonry ? Is he ignorant of the fact that Mr. Buck has sur- 

 mounted this difEculfy by the simple expedient of adjusting the angle 

 of intrado — or is it that, rather than acknowledge his inferiority, he 

 persists in what he knows to be wrong, and addresses bis book to the 

 working classes in the hope of escaping detection ? 



Again, with reference to obtaining the angles between the joint lines 

 in the face and in the soifit of the arch. It is perfectly distressing to 

 see a problem which admits of easy solution so miserably mutilated 

 as it is in his hands. The construction given by him, that is to say 

 the on'y one that deserves the name of an approximation, occupies 

 two and a half closely printed pages of his book, while these angles 

 may be obtained with much greater accuracy, and with about a quarter 

 of "the labour as follows. Let A D B 6g. 2 be the elliptical face of 



