Now, as there are always a great many parts of this invisible matter that enter and circulate in the pores of hard bodies they not only make them hard, as we have just explained, but furthermore they are the reason why some spring back and return to their original shape, others remain bent, and still others are fluid and liquid; and finally, they are the cause not only of the strength found in the parts of hard bodies for remaining beside each other but also of that found in the parts of fluid bodies for separating from each other;.e.