A quotation from J. T. Desaguliers, one of the foremost scientific lecturers in England until his death in 1744, contrasts the use of demonstrations to show physical principles and those designed to imitate real situations:
I have indeed a Machine with brass wheels whose steel axes have very small pivots nicely made that any of the wheels set in motion will turn for the space of more than half an hour… but the use of my machine being chiefly to show how near these kinds of experiments may be brought to agree with a mathematical theory; we cannot expect that any carriage to bear weight can have so little friction. Therefore I choose to relate Monsieur De Camus's Experiments made on Models of Carriages of an inch to a Foot every way representing Carts and Waggons… because it shows us directly what is the real Friction in the carriages at present in use.