f. AGbaas 
XXXV. On a correct practical Method for cutting Spherical 
Brick Niches—On the Spiral Line—and On Spandrel Groins. 
By Mr. Ricuarpd Brown, of JVells-Street, Oxford-Road. 
I. On Spherical Brick Niches. 
F ROM my never having seen in any publication hitherto, a 
correct practical method for cutting spherical brick niches (a 
thing so essential) I was induced to send for insertion in your use- 
ful Magazine the accompanying plate. It contains an accurate 
drawing of the moulds and templets as used for gauging the 
bricks in the head of the niches recently executed in the north 
flank of Drury Lane Theatre: therefore these lines may safely be 
depended on when applied to all such future works. 
I am, sir, 
Yours respectfully, 
February 1816. RicHaRD Brown. 
— a 
On Spherical Niches, Plate lf. fig. A. 
First describe the curvature of the plan with the radii sé, suv, 
then mark the bricks on it, beginning at the front with a header 
as ¢,and then with astretcher as J, and so on alternately. The plan 
eing now laid down, next project the orthographical elevation gg 
from the plan, and from thence proceed with the divisions of the 
bricks round the head of the niche, observing that the joints must 
always be so arranged as to have a brick fall directly over the 
centre of the niche, as k: this is called the key of the arch. 
The bricks are next radiated to the centre of the niche,and the 
heading joints described concentric to each other, which com- 
pletes the construction of the niche. Next for the moulds :— 
First form the centring, as shown by the orthographical elevation 
ghg (which is sufficiently explicit without detail); then from 
qq bring down the lines to 47, and on-r with the radius rm again 
describe the plan of the niche on which are shown the ichnogra- 
phical appearance of the centring and some of the radiating lines 
of the brick-work. These lines, which are to be the guide in 
laying the bricks on the centring, are projected ichnographically 
on the centring, in the following manner: First, describe the 
arch m5, &c. equal to the rise of the niche head ; and for plainer 
inspection, suppose the arch to contain but five bricks round 
the head, which arch is here divided into five equal parts, as 
shown by the numerical figures: next divide half the plan into 
four equal parts or more (at discretion): these four divisions are 
then to be drawn parallel to rz, and from 1 234, lines are to 
Vol, 47. No. 215. March 1816, L be 
