450 PHILOSOPHICAL TRANSACTIONS. [aNNO J 778. 



This attention is equally necessary for the 2d layer of laths hereafter mentioned 



(^ 15). 



^ 15. This first layer of laths ought to be covered with a pretty thick coat of 

 the same rough plaster spoken of above (^9)- A 2d layer of laths ought then 

 to be nailed on, each lath being, as it is put on, well squeezed and bedded sound 

 into the soft rough plaster. For this reason, no more of this first coat of rough 

 plaster ought to be laid on at a time than what can he immediately followed with 

 the 2d layer of laths. The laths of this 2d layer ought to be laid as close to 

 each other as they can be, to allow of a proper clench for the rougti plaster. 

 The laths of the 2d layer may then be plastered over with a coat of the same 

 kind of rough plaster, or it may be plastered over in the usual manner. 



^ l6. The 3d method, which is that of inter-securing, is very similar, in most 

 respects, to that of under-flooring; but no sand is afterwards to be laid on it. 

 Inter-securing is applicable to the same parts of a building as the method of ex- 

 tra-lathing just described; but it is not often necessary to be used. 



§ 1 7. His lordship made a great number of experiments on every part of these 

 different methods. He caused a wooden building to be constructed at Chevening, 

 in Kent, in order to perform them in the most natural manner. The methods 

 of extra-lathing and double under-flooring were the only ways used in that 

 building. 



On the 26th of September 1777, Lord M. repeated some of his experiments 

 before the president and some of the fellows of the r. s., the Lord Mayor and 

 Aldermen of the city of London, the committee of city lands, several of the 

 foreign ministers, and a great number of other persons. 



^18. The first experiment was to fill the lower room of the building, which 

 room was about 26 feet long by \6 wide, full of shavings and faggots, mixed with 

 combustibles, and to set them all on fire. The heat was so intense, that the 

 glass of the windows was melted like so much common sealing-wax, and ran 

 down in drops; yet the flooring boards of that very room were not burnt through, 

 nor was one of the side timbers, floor-joists, or cieling-joists, damaged in the 

 smallest degree; and the persons who went into the room immediately over the 

 room filled with fire, did not perceive any ill effects from it whatever, even the 

 floor of that room being perfectly cool during that enormous conflagration im- 

 mediately underneath. 



§ 19. He then caused a kind of wooden building, of full 50 feet in length, 

 and of 3 stories high in the middle, to be erected, quite close to one end of the 

 secured wooden house. He filled and covered this building with above 1 100 

 large kiln faggots, and several loads of dry shavings, and he set this pile on fire. 

 The height of the flame was no less than 87 feet perpendicular from the ground, 

 and the grass on a bank, at 150 feet from the fire, was all scorched; yet the 



