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July, 1909 barge taking a sheer in crowded or narrow channels, and caused a need- less consumption of steam in recover- ing the line thus payed out. The small cylinder ports choked back the steam entering and leaving the cylin- ders, raising the back pressure as well as lowering the initial pressure when recovering the line, thus adding to the steam consumption. In paying out rapidly (at which time the most resisting power is necessary) the small ports prevented the steam from filling the empty cylinder, after the piston reversed, in time to offer the maximum resistance. Quick Opening Automatic Valve. In towing machines built under later patents of Messrs. Metcalf and Dalg- leish, these features have been more or less gradually discarded in favor of a quick-opening automatic valve and very large cylinder ports. In these machines as now built the auto- 'matic valve is fully opened in about two-fifths of a revolution of the drum. The steam going through the large , cylinder ports fills the cylinders very quickly and opposes throughout the stroke as high resistance to paying out as it is possible to furnish. As soon as' the engine begins to take in line, the automatic valve closes part way, leaving sufficient opening for ordinary working speed, but not enough to allow the engine to run away and wreck itself under no load. Thus the admission is throttled but the, back pressure does not rise at ey same rate as with small cylinder ports, and as a consequence less steam is used. To farther reduce the amount of steam used and to minimize the temptation to tow on a rigidly set brake, these machines are now being supplied with spring set brake bands Operating on the principle above de- scribed. In this connection it may be stated that as far as our knowledge goes nearly every accident to towing machine or hawser has been due to towing on a rigidly set brake. Cer- tainly more accidents have been due to this one cause than to all others combined, A range of pay-out and recovery of 36 to 45 revolutions of the drum is Probably sufficient for any emergencies likely to arise. Determining 'Drum Capacity. The drum capacity for a given size of line is determined by the demands of the trade and not so far as we know by any theoretical or practical formula. In changing over from "TAE Marine. REVIEW bitted manila lines to wire lines with automatic towing machines, the previ- ous necessity for a very long manila line to give the required stretch causes a strong prejudice in favor of a very long wire line, and it nas been easier to furnish machines for the length of line demanded than to make any very serious attempt to overcome the old prejudice. Some users have gradually shortened the distance between barge and steamer until they use only half or less than half the line on the drum. So long as the take-up of the dip, and the stretch of the line cannot be relied upon to give the required increase of span and an automatic towing machine is necessary, a large dip can scarcely be considered ad- vantageous. There does not appear to be any available data concerning the power consumed in dragging the line through the water, but this factor probably much more than counter- balances any theoretical economy as- sumed on the ground that the machine will not have to operate so much of the time as with a small dip. It seems to the writer, therefore, that when a towing machine is installed and prop- erly operated the tow line should be as short as certain practical considera- tions will allow so that the drag of the line may be reduced to a minimum and the machine and line may not be unnecesarily expensive (Note g). With an extremely short line the wake from the steamer would affect the barge, steering would be more difficult, and there might be danger of the vessels fouling. The effect of the wake appears to be a somewhat mooted question and the writer has suggested, as a basis for possible dis- cussion, the arbitrary rule that the length of line in feet be made 600 times the diameter in inches and that one-third of this length be held in re- serve on the drum, and be the range of automatic pay-out and recovery of the machine. Suggestions or data bearing on this. subject would be very acceptable. Government Regulations of Tows. Long tows are a serious menace to other vessels navigating the same wa- ters and the government regulations which went into effect Feb. 1, 1909, prescribe in part as follows: 1. "Tows of sea-going barges navi- gating inland waters of the United States are limited in length to four vessels, including the towing vessel or vessels." 2 "Hawsers are limited in length to 75 fathoms, measured from the stern of one vessel to the bow of the Z0/: following vessel and should in all cases be as mutch shorter as the weather and sea will permit." Most of the vessels at which this legislation was aimed use manila lines operated by steam gypsies. When it becomes necessary to shorten hawser the steamer must slow 'down and each barge takes in the slack as it overhauls the vessel ahead. This operation is laborious and involves a needless loss of time. The adoption of towing machines would save both of these items and the decrease in cost of lines would in a few seasons pay for the machines. Of vastly greater importance, however, is the fact that towing machines enable them to operate in rough weather with much shorter lines than could other- wise be used and so diminish the danger to other vessels as well as to themselves, 'Indicator Cards of Iroquois. Mr. Wilkie has kindly furnished some indicator cards taken from the 18 x 20-in. towing machine on the steamer Iroquois, while in actual service. This machine carries 3,200 ft. of 2%-in. diameter wire line, which was originally shackled to the line from a similar en- gine on the barge Navahoe. The lines are now used in parallel, the free end of each being made fast to a towing hook on the other vessel. This allows the reducing valves to be set for a lower pressure, lowers the stress on each line and reduces the length of the tow, and the dip of the line. The shackle caught on the bottom at one time previous to this while crossing the Grand Banks. The machine was towing on the automatic and no damage was done. The auto- matic valve movement on this machine is not so rapid as on those built later, and the machine is not equipped with the spring set brake which was de- veloped later, but the cards may be of interest as the first that, to our knowl- . edge, have been taken from a towing machine in actual service. In the original cards all lines are full and in same cases rather faint. Plate 1 and Plate 2 are made from tracings of the original cards, in which 'those lines which appear to have been made while the engine was being overhauled are traced dotted, except in Fig. 3, Plate 2, where the card has been traced with all lines full exactly as in the original. Parts of Card Traced Separately. The parts of the continuous card on Plate 1 have been traced separately and lettered for reference. The same