332 Memorandum regarding Syrian or Cylinder Boofs, [April 



and to beat into the interstices as much brick, jelly, and chunam as 

 possible, to render the mass compact. Over the cylinders thus packed, 

 chunam well diluted is plentifully spread ; and on the summit of the 

 arch in large curves, a sufficient quantity of jelly and chunam is laid 

 to raise that part a little, and thus to prevent the lodgment of rain and 

 moisture. Two coats of flat tiles in chunam are afterwards placed over 

 the arch and the exterior polished with fine chunam. The haunches 

 being about 15 or 18 inches thick in circular spans, and more in others, 

 the lower portion of the cylinder arches will need to be thickened with 

 jelly, or brick, and chunam,to produce an uniform slope in the the extra- 

 dos before the flat tiles are placed. The centreings should not in 

 fny bumble opinion be removed before the arch is thoroughly dry^ 

 for the materials being slight, and fragile while wet, a sudden settle- 

 ment at that time is very dangerous, and much more mischief is to be 

 apprehended than from any slight improbable sinking of a well turn- 

 ed curve composed of light pottery, extremely strong when dry and 

 surrounded, as it will be then, by firm cement, and upheld as it were by 

 the outer coatings of an equally powerful substance. The reasons which 

 prompt the speedy removal of centreings to heavy stone and brick 

 arches, do rtot here exist, and as with the common native centreings of 

 mud, the gradual sinking of the various parts can and does take place 

 during the construction, from the flexible nature of such supports, I cer- 

 tainly prefer them for cylinder roofs. The centreings used at Bangalore 

 were of the roughest kind and apparently very weak ; indeed [on one 

 occasion during my absence, so careless were the workmen on this 

 point that a failure of one, before the work was dry, caused the ruin 

 of a large arch and the irreparable injury of the outer verandah. The 

 centreings were principally composed of crooked old bamboos laid 

 over and tied to jungle-wood Malabar trusses, supported on sun-burnt 

 brick and mud pillars — sun-burnt bricks were packed closely together 

 on the bamboos, earth strewed on these, and a plaster of wet mud 

 applied over all to render the curve smooth, which was further effect- 

 ed by a coating of dry sand. Strong posts of timber are preferable to 

 the weak brick and mud pillars, and the trusses are about nine feet 

 apart. When the centreing is to be removed, the bricks and earth 

 along the middle of it, that is immediately under and near the key 

 stone, should be carefully picked out first, and cleared away from be- 

 tween the bamboos ; then equal portions on either side simultane- 

 ously to a distance of about three feet, after which the whole may be 

 rapidly taken down. As a proof of the vast strength of these cylinder 

 jroofsj I must record the fact? that, on two occasions, owing to heavy 



