Did you ever try to measure a smell? Can you tell whether one smell is just twice as strong as another. Can you measure the difference between one kind of smell and another. It is very obvious that we have very many different kinds of smells, all the way from the odor of violets and roses up to asafetida. But until you can measure their likenesses and differences you can have no science of odor. If you are ambitions to found a new science, measure a smell.

'Discovery and Invention' by Alexander Graham Bell, The National Geographic Magazine, Vol. 25 (1924)