VOL. LXVIII.] PHILOSOPHICAL TRANSACTIONS. 447 



XXXIX. Chemical Experiments and Observations on Lead Ore. By Richard 



fVatson, D. D., F. R. S. p. 863. 

 Reprinted in Bishop Watson's Chemical Essays. 



XL. Description of a most Effectual Method of securing Buildings against Fire, 

 Invented by Charles Lord Viscount Mahon,* F. R. S. p. 884. 



^ 1. This new and simple method may be divided into 3 parts; namely, under- 

 flooring, extra-lathing, and inter-securing, which particular methods may be ap- 

 plied, in part or in whole, to different buildings, according to the various circum- 

 stances attending their construction, and according to the degree of accumulated 

 fire, to which each of these buildings may be exposed, from the different uses 

 to which they are meant to be appropriated. 



§ 2. The method of under-flooring may be divided into 2 parts, viz. into single 

 and double under-flooring. The method of single under-flooring is as follows. 

 A common strong lath, of about J- of an inch thick, either of oak or fir, should 

 be nailed against each side of every joist, and of every main timber, which sup- 

 ports the floor intended to be secured. Other similar laths ought then to be 

 nailed the whole length of the joists, with their ends butting against each other: 

 these Lord M. called the fillets. The top of each fillet ought to be at 1± inch 

 below the top of the joists or timbers against which they are nailed. These fillets 

 will then form, as it were, a sort of small ledge on each side of all the joists, 



^ 3. When the fillets are about to be nailed on, some of the rough plastef 

 hereafter mentioned must be spread with a trowel all along that side of each of 

 the fillets, which is to lie next to the joists, in order that these fillets may be well 

 bedded in it when they are nailed on, so that there should not be any interval be- 

 tween the fillets and the joists, 



§ 4. A great number of any common laths, either of oak or fir, must be cut 

 nearly to the length of the width of the intervals between the joists. Some of 

 the rough plaster referred to above (§ 3) ought to be spread, with a trowel, suc- 

 cessively on the top of all the fillets, and along the sides of that part of the 

 joists which is between the top of the fillets and the upper edge of the joists. 

 The short pieces of common laths just mentioned ought, in order to fill up the 

 intervals between the joists that support the floor, to be laid in the contrary direc- 

 tion to the joists, and close together in a row, so as to touch each other, as 

 much as the want of straightness in the laths will possibly allow, without the 

 laths lapping over each other; their ends must rest on the fillets spoken of above 

 (§ 2) and they ought to be well bedded in the rough plaster. It is not proper to 



* Now (1807) Earl Stanhope. 



