“Mr. Rapp, what is the difference between an element and a compound body?”
Mr. Rapp is again obliged to confess his ignorance.
“A compound body is composed of two or more elements,” says the grinder, “in various proportions. Give me an example, Mr. Jones.”
“Half-and-half is a compound body, composed of the two elements, ale and porter, the proportion of the porter increasing in an inverse ratio to the respectability of the public-house you get it from,” replies Mr. Jones.
The professor smiles, and taking up a Pharmacopœia, says, “I see here directions for evaporating certain liquids ‘in a water-bath.’ Mr. Newcome, what is the most familiar instance of a water-bath you are acquainted with?”
“In High Holborn, sir; between Little Queen-street and Drury-lane,” returns Mr. Newcome.
“A water-bath means a vessel placed in boiling-water. Mr. Newcome, to keep it at a certain temperature. If you are asked at the Hall for the most familiar instance, they like you to say a carpenter’s glue-pot.”
And in like manner the grinding-class proceeds.