364 



The board re- 

 moved two feet 

 farther, and 

 another layer 

 formed ; 

 and this repeat- 

 ed till the space 

 i» covered. 



Every portion 



must be well 



united, 



and the whole 



finished in a day 



if possible. 



Ten days after 

 the vacuity 

 filled up. 



Will last 150 

 years, 



and then may 

 be taken up, 

 burned afresh, 

 and laid down 

 again. 



Will then last 

 as long as 

 before. 

 Quantity of 

 materials and 

 labour. 



PLASTER THRESHING FLOORS. 



to guard against the inconveniences that would ensue from 

 the plaster swelling when in contact with both walls. This 

 space may be three inches in a length of twenty feet. 

 Other layers of plaster are then formed in succession by 

 the side of this, bounding them always by the long ruler, 

 placed at two feet distance from each preceding layer, which 

 will keep them all of an equal thickness ; and thus the 

 whole of the lloor is completed. 



Great care must be taken, that the successive portions 

 unite well together, that there may be no vacuity between 

 them. For this purpose it is necessary to finish the whole 

 in one day if possible: and to accomplish this a sufficient 

 number of men should be employed in diluting and pre- 

 paring the plaster, that those who are forming the floor 

 may proceed without interruption. 



Ten days afterward the vacuity left between the floor 

 and the wall is filled up, and then it will be ready for use. 

 If in this time it acquire a deep red colour, it is a good 

 sign. Such a floor will last in common a hundred and fifty 

 years ; and still longer, if it be not exposed to damp. 

 When its surface becomes injured by time, and is no longer 

 as smooth as it ought to be, all the plaster may be removed, 

 exposed to the weather for a fortnight, burned again as if 

 it were fresh taken from the quarry, pounded, mixed with- 

 water, and relaid in the same place, proceeding exactly in 

 the same manner as when it was laid down the first time. 

 The floor thus remade will last a;* long as it did before. 



The advantages of such a floor may readily be conceived, 

 when the high price to which timber has risen of late years i± 

 considered. That some calculation of its cost may be. 

 formed, a square fathom of this floor, three inches thick, 

 will require about eleven hundred weight of gypsum ; and. 

 two men can work up seven times this quantity in a day. 



SCIENTIFIC 



