would become the top, and the top would become the bottom : and this is called the topsey-turvey mode, which is nearly allied to the accidental, and frequently arises from it.
Prof.Very good — But are not salt-boxes sometimes single and sometimes double?
Stu. Yes.
Prof. Well, then mention the several combinations of salt-boxes with respect to their having salt or not.
Stu. They are divided into single salt-boxes having salt ; single salt-boxes having no salt ; double salt-boxes having salt ; double salt-boxes having no salt ; and single double salt-boxes having salt and no salt.
Prof. Hold ! hold ! — you are going too far.
Gov. We cannot allow further time for logic, proceed if you please to
NATURAL PHILOSOPHY.
Prof. Pray Sir, what is a salt-box?
Stu. It is a combination of matter, fitted, framed, and joined by the hands of a workman in the form of a box, and adapted to the purpose of receiving, containing, and retaining salt.
Prof. Very good — What are the mechanical powers concerned in the construction of a salt-box?
Stu. The ax, the saw, the plane, and the hammer. . . .
Prof. . . . Have not some philosophers considered glue as one of the mechanical powers?
Stu. Yes ; and it is still so considered, but it is called an inverse mechanical power : because, whereas it is the property of the direct mechanical powers to generate motion, and separate parts ; glue, on the contrary, prevents motion, and keeps the parts to which it is applied fixed to each other. . . .
Prof. Is the saw only used in slitting timber into boards?
Stu. Yes, it is also employed in cutting boards into lengths.
Prof. Not lengths : a thing cannot properly be said to have been cut into lengths.
Stu. Into shortnesses.
Prof. Certainly — into shortnesses. Well, what are the mechanical laws of the hammer?
Gov. The time wastes fast ; pass on to another science.
Francis Hopkinson, Miscellaneous Essays (Philadelphia, 1792), I, 340-349 passim.
