^84) Mr Low‘*s Description of a Machine for Raismg Stones. 
6troke or two of a hammer will do so with ease. Doubtless the 
force with which the iron is retained, will diminish with the elas- 
ticity of the stone ; so that it will be vastly less in the softer 
stones, as in freestone, than in granite, marble, and the like. 
Indeed, T believe it is only in the latter species of stones that the 
experiment can be made with effect. 
A person might conceive how a large mass of stone might be 
held suspended, in certain cases, in the manner before adverted 
to ; but we cannot account for masses being raised in this man- 
ner from every variety of horizontal and inclined position ; nor 
conceive how, if this were the mode in which the two bodies 
were kept attached, it should happen, that while no constant 
force that can be exerted, in whatever direction, will loosen the 
little piece of iron, the force of percussion will do so at once. 
Let any one procure a plug of the form described, and attach 
it in the manner mentioned, to a mass of granite, and, instead 
of using machinery, let him pull the rope with the hand in any 
direction, and he will as soon move a tower from its base as the 
little plug from its position ; so certainly is it the grasping of the 
stone, and not the direction in which the rope is pulled, that 
keeps the mass attached. In making the experiment with the 
machine, it is even necessary to be careful that the hole shall be 
made as perpendicular as possible ; for, if made in the direction 
represented by the plugs A or B, in Fig. 2., that part of the 
stone is apt to give way which lies between the iron and the sur- 
face. We shall often be surprised, in trying the experiment on 
large pieces of granite, to observe with how slight a seeming 
hold of the stone the masses will be torn up. Sometimes the 
iron-pin is not driven above the fourth part of an inch into the 
stone before it becomes immoveable, and capable of raising a 
weight of many tons from the earth. 
When we consider the greatness of the elastic power of 
granite, as shown by the simple experiment in question, we may 
perhaps wonder, that the ingenuity of man has not hitherto more 
applied so surprising a property to practical uses. It appears, 
that, with a little piece of iron driven into a stone, with a force 
which a child might exert, the largest vessels might be moored ; 
that by the same means masses of granite might be nailed, as it 
