NATURAL PHILOSOPHY. 179 



It follows from, this experiment that to draw a rough stone upon a firm 

 and smooth bottom there is needed a little over ?. of its weight; !-, if the 



& 



surface is of wood; |, if the movement is made of wood upon wood; and if 

 the two sliding surfaces of wood are soaped, but . But if we use rollers 

 placed immediately between the stone and ground there will be required a 

 little over ^ of the weight, and ^ if they roll upon wood; and, finally, if 

 they roll between two smooth wooden surfaces there will be needed but 

 about the ^ of the weight. 



Still it is proper to remark, that as woods compress under great loads, the 

 rollers made of this material are subject to a change of form, to be crushed, 

 and to sinking in the pieces between which they are placed. This produces 

 a friction, whose cifect increases Avith the load. To raise the obelisk at the 

 square of St. Peter's, in Rome, which, with all its fixtures, weighed 829,250 

 pounds, there were required forty capstans, and to draw it upon a horizontal 

 plane with rollers placed between two wooden surfaces it only needed four; 

 whence it follows in this case that the force was but the ^ part of the 

 weight, while the experiment above cited gives a little over the Jj part. 

 But Fontana, who superintended this operation, observed that most of the 

 rollers, which were seventy in number, were crushed, and that the others 

 sank into the pieces of wood between which they were placed. 



To have the full benefit of the rollers they should be as incompressible as 

 the surfaces between which they move. Granite rollers, between surfaces 

 of the same material, to prevent breaking should be very short, and their 

 number great, to have as little of the load as possible on each. The length 

 should not be over one and a half diameters. When the stone has consider- 

 able width they must be set in many rows. This method, if practicable, 

 would have been preferable to the balls which the Count of Carbury used 

 for the transportation of the rock which served for the base of the equestrian 

 statue of Peter the Great; they required the ^ part of the weight. 



From the results of these experiments, and the observations to which they 

 give rise, we may calculate the force required to transport the stone which 

 formed the monolithe structure at Sa'is, and the covering of the temple at 

 Buto. 



Experience with works has taught us that a man of medium strength, and 

 used to work like those employed by the ancients, can carry a load equal to 

 his weight, and haul one and a half times as much; so that for the stone 

 cover of the temple at Btito, whose weight we have estimated at l,98i,950 

 pounds, there would be required 10,000 men to draw it upon a smooth and 

 solid ground; 9000 to draw it upon a surface formed of pieces of wood; 

 8333 if the stone was put upon a wood platform and drawn upon wood; and 

 only 2500 men if care was taken to soap the two surfaces which slid upon 

 each other. 



The block being 52.8 feet wide, the men could easily be disposed in forty 

 rows, which for the first case would require 250 in each row, in case they 

 were equal, and much less if they diverged; 225 for the second; 208 for the 

 third; and 62 for the fourth : the last is the most practicable method. 



The great breadth of this stone and its weight would make it impossible to 

 use wooden rollers. As for those of granite, if the ground were firm and 

 smooth enough to make use of them, 300 men, or seven and a half rows, 

 would have sufficed to move the load. But it is not likely that this method 

 was adopted, on account of its great expense. It is much more probable 

 that they made use of capstans. 



