PRACTICAL AND THEORETICAL SYSTEM OF ARITHMETIC, CONTAINING A NEW SYSTEM OF PROPORTION; WITH "THEORETICAL EXPLANATIONS OF ALL THE PRINCIPAL RULES. BY GEORGE WILLSON. FIFTH EDITION, REVISED AND CORRECTED. CANANDAIGUA. PUBLISHED AND SOLD, WHOLESALE AND RETAIL, BY C. MORSE. BOLD ALSO BY F. J. HUNTINGTON & CO., NEW YORK; OLIVER |