The variety of measures employed by different nations renders medical directions often obscure, and occasionally fallacious. The word mensura is sometimes employed absolutely to denote a given bulk, and the measure occasionally contains one, sometimes two, quarts, and the quadrans mensurae is either six or twelve ounces. The great diversity in this respect has induced the London college to order every thing by weight; for a pint of the purest alcohol is very different from even a pint of water, and much more so from a pint of the vitriolic acid. In general, the pint is supposed to be equivalent to a pound; but, in medicinal directions, it is estimated at twelve ounces: the French pint is double, and the Scotch pint equal to two quarts. The cantharus of the Swedes equals five pints.

In smaller quantities, the tea spoonful is estimated as equal to a drachm, but few tea spoons hold more than forty drops. A dessert spoon holds somewhat more than than two drachms, called, in prescriptions, cochleare medium, and the table spoon about half an ounce. The modern French weights and measures are greatly

6 I 2 changed, and have produced no little confusion in medicine, chemistry, and even in common life. We shall detail the principles of their new system under the article Pondera, on which that of their measures depends; so that we shall ill this place only explain the terms. The fundamental measure, the litre, filled with distilled water, is equivalent to the Paris pint, somewhat more than two English pints, and, in weight, is nearly equal to the kilogram, two pounds. The semilitrum (demilitre) is equal to somewhat more than a pint; the decilitrum to about three ounces, and a drachm, equal in weight to the hectogram: the double and the half of the decilitrum are easily estimated. The litre contains fifty cubic inches, and consequently the centilitrum half a cubic inch; and the double cen-tilitrum one cubic inch, or nearly five drachms, about a large table spoonful.