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208 has been done for Fig. 1, Plate 2 The following probably describes with fair accuracy what took place while the card on Plate 1 was being made: The series opens with the machine paying out, the pressure rising and the cranks approaching their most effective position. For an instant the engine stops, then winds in an inch or so of line, but the load increases and finally runs the engine backward. The point where the pressure drops, making a dip in the upper line, is the place where the other piston reverses, and takes some of the steam out of this cylinder to help fill the other. The pressure then rises due to the steam coming in through the inlet pipe and due to the compression as both pistons advance. The next card, bec 15 very similar to. it, 'but here the recovery took place in the same position in the other cylinder at which it occurred the first time in this cylin- der so that the engine started to wind in when the piston was a little past the half stroke position instead of near the beginning. Again the load overpowered and it paid out for the balance of the stroke. This partia) stroke was evidently so timed that it hit the knocker twice and jumped the indicator about 1% in. instead of one. im the next card; c-d, the en- gine winds in for almost a full stroke and then pays out again, but the steam is in the other end of the cylinder and this end is open to exhaust. Just before the other end of the stroke was reached, the load overpowered again and the line paid out. In the next card, d-e, there was a pause and a little recovery beyond the three- quarter stroke position, then toward the middle of the back stroke the load fell off again and the engine started to wind in. The next card, e-f, is a typical struggling to wind in card. The admission rises sharply, then the pressure falls off slightly until the other piston gets to about the dead point, when the engine stops. The steam pressure then rises until the load begins to yield, then again in several jumps until the other crank gets in a better position to assist or the load falls off and the engine starts to wind in again.. Ihe next, f-g, is very like it, but here instead of the engine gain- ing after it stopped until the other crank got to work, it lost and moved backward a little way. A somewhat similar process taking place in the other cylinder, is indicated at the bottom of this card. The next card, g-h, is also similar, still winding in, losing a little at the middle position, then completing the stroke. TAe MarRINE REVIEW The next card, h-i, starts in the same way, but after jiggering a while, the load finally overpowers the engine and the line starts out. The next three cards are characteristic pay-out cards, though at one place in j-k it stopped and took in a trifle. In the card J-m, near the most effective crank position, the engine overpowered the load. The next card, m-n, is also a take-in card. The little lift that shows near one end of the back pres- sure line on the take-in cards is where the other cylinder opens to exhaust and raises the back pressure. in the card n-o the engine pays out, the steam being in the other end of the cylinder. In the card o-p the engine overpowers the load and winds in with the steam in the other end and the same characteristic rise in back pressure shows when the other cylinder exhausts. Fig, 1, Plate, 1, shows the card p-q (a characteristic take-in card) in full lines together with p-q dotted lines, as the assumed card for the other end of the cylinder. At the right are shown the corresponding' tangential pressures for one revolution. The full line above is the stroke over and the dotted line below is the re- turn stroke. These are rectified (dot and dash lines) and the combined tangential pressure for one complete revolution is shown as a full line in Fie. la, The same process is repeated for the characteristic pay-out card, 2-r, also for a maximum pay-out card taken of1. a different date. The back pressure on the pay-out cards, when open to exhaust, shows the back pressure in the line due to the other auxiliaries. Pig. |, Plate 2, 18 imteresting in that it shows in parts of some of the pay- out cards a higher pressure than that in the admission pipe. This appears to be due to the line paying out so rapidly that even with the large cylin- der ports there is some back pressure in the cylinders due to the rapidity with which the pistons force the steam back into the pipe after it has filled the cylinder at. admission pipe pres- sure. Interpolates a Correction. (At this point in reading his paper Mr. Kemble interpolated the following correction: I met Mr. Wilkie when the Iroquois was last in port and asked about the steam pressure during the time that the cards on Plate 2, Fig. 1, were be- ing taken. He stated that the steering engine was connected with the same steam and exhaust line as the towing reversed in- another paying out. July, 1909 machine, and that the average pressure as shown by the gage was about 125 Ib. as reported, but that it might have risen as high as 145 lb., when neither engine was in operation. As the tow- ing machine does not take steam when paying out, this tends to cast some doubt upon my _ statement that the pressure in the cylinder during parts of the pay outwards was higher than that in the admission pipe, since the margin between 145 Ib. and the highest pressures indicated is only three or four lb., and this might possibly be due to inaccuracies in the instruments. The evidence would indicate, however, that the pressure in the cylinders was actually greater at times tnan that in the admission pipe, though the differ- erce is not nearly so great as at first appeared. ) Fie. 2, Plate 2 did not have aay atmospheric line. It begins with the end of a series of take-in cards and contains a complete series paying out, one taking in and the beginning of This shows the more regular action which accom- panies a following sea where the in- terval between the waves is greater than, with a head sea. Fig, 3, Plate 2, was taken towing with two hawsers. With this method of towing it was found to be possible to reduce the pressure in the admis- sion pipe to 80 pounds and thus. to reduce the stress in the line and ,tc shorten the length of the tow without sacrificing any advantage whatever. These cards would be more valuable if we were able to know the time element throughout. The difficulty of obtaining this aboard ship will be readily appreciated, but the writer hopes to be able at some future time to make report on similar cards with this factor included. He wishes to here express his ap- preciation of Mr. Wilkie's hearty co- operation, and also of the assistance of Mr. Henry Penton while this pa- per was in preparation. Notes. (a) This loss is probably consider- able with tow lines of extreme length, and should not be lost sight of in con- sidering the proper length of tow line for any given case, There appears, however, to be.no definite data on the subject, and for this reason it is ar- bitrarily neglected in this problem. (b) In order to facilitate the study of this and other problems involving the properties of the catenary the writer has constructed the _ catenary charts which are appended, and which he hopes may be of service to others,