horses on canals. We see the New York and Albany tow-boats, with from twenty to forty loaded canal boats, running at four miles per hour, and they have taken over sixty boats in a single tow from New York to Albany. But an engine, with a respectable part of their steam, can take but a _small fraction_ of their boats, and at a largely reduced speed on the canal. The doom of 1845, of 1858 to '62, and of 1871 to '72, hangs over steam like a shroud; it is a mechanical doom. Steam should be mechanically elevated so that it can utilize from a third to half of its power, and so that an engine can develop an equivalent of thirty to fifty horses on the tow-path to a train of boats, and so that it can take trains of ten to fifteen boats on the two sixty-miles levels--where large hulls can be built and used without necessity of passing locks--and somewhat smaller trains on the other parts of the canal, averaging eight to ten boats per tug, or moving from 70,000 to 80,000 bushels of corn, all as fast as they can be safely handled, and then the day of horses is limited, and canals will need new arrangements, new regulations and new customs. Tugs on the canal have never exceeded a utility of eight to fifteen per cent. of the inherent power of their steam. Hence, they have never had towing power to develop the movement of trains of boats; but when they can be made mechanically to utilize from thirty to fifty per cent., the train movement becomes initiated with boats just as absolutely as with cars, and the tow-boat system will be just as prominently and universally established between Buffalo and Albany as it is between New York and Albany. It is perfectly practical for steam, when it shall possess a respectable mechanical adaptation to canal duty; that is, when it shall not be so shamefully profligate in expenditures of power--_to double the average speed of horses, or lessen the general average of ten days on the canal to five days_, of which the down trips may overrun and the up trips fall short, as with horse average. When a single tug shall equal 30 to 50 horses on the tow-path, it equals 60 to 100 of supply, as all require the alternate team. The automaton system of steam is a hinderance to horse-boat navigation, besides increasing the risks and dangers, whilst the towing system, in substitution for horses, greatly improves the navigation and lessens the risks and dangers. Averaging the total mileage of a season with horse-boat times of transit, and boats meet each other every twenty minutes, night and day including Sundays, for seven months. To carry this tonnage, there must be eleven meetings of steamers to nine by horses, which increases the risks and dangers twenty-two per cent.; on the other hand, tows to the same tonnage would only meet each other about every three hours, hence for long distances they have an unobstructed water way. MECHANICAL INVENTION, to adapt steam to the heavy resistances of canal boats, is therefore the first and greatest necessity of canals.