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got ready; consequently, another cave may be prepared in the same manner as the former one; with this exception only, that, instead of filling up, or supplying the second cave with pure water, let it be run through the former cave first, and then put upon the second. The intention of this is obvious; that, while the last is supplied with water, the remaining strength of the first is extracted, and collected into the second; and this must be the uniform practice at all times, that none of the alkali be lost; never turning out a cave, as spent, until you discover by the test the alkali is vanished.
Having just mentioned the test, I shall take this opportunity of explaining what it is.
The test is a thing so necessary for a soap-boiler, that it is impossible for him to conduct his operations with propriety without
