THE EXPERIMENTS OF 1836. 97 



vessel. When the horses had arrived at that end of the station from which the 

 vessel had commenced its motion, the vessel had reached the point from which 

 they had started. 



The apparatus was now ready for the succeeding experiment, one end of the 

 rope being at the pyramid and the other at the starting-point. The vessel was 

 immediately drawn back to the starting-point while the horses were returning to 

 the pyramid, and being again attached to the extremities of the rope, the next 

 experiment was begun. 



It was found that considerable time elapsed before the vessel attained the 

 uniform velocity due to the moving force, and therefore the vessel was put in mo- 

 tion through a considerable space previous to making the observations. Where 

 this proved inconvenient, a very simple mode was used of attaining a higher ve- 

 locity, which was by the attachment of an additional weight (F) by a rope about 50 

 feet long to the former weight in the pyramid, so that this weight should rest on 

 the ground, unless the principal weight were raised to a height greater than 5 

 feet, in which case alone the additional weight would be called into action. By 

 this means it was easy, on commencing the experiment, to keep the principal 

 weight so high as to raise the additional weight to produce the required accelera- 

 tion, and afterwards, before commencing the observations, to allow it, by resting 

 on the ground, to cease from acting on the vessel. The velocity due to the moving 

 force was thus attained in a shorter time than would otherwise have been neces- 

 sary. 



The observations were made in the vessel upon time and resistance, the rope 

 through which the propelling force was applied being attached to the vessel by 

 the hook of an accurate spring dynamometer, indicated the resistance in pounds, 

 and accurate chronometers gave the time. One observer being placed so as to 

 have a line of sight at right angles to the line of motion, communicated by sound 

 the instant of passing the rods placed at equal distances along the bank, and at 

 the same instant the time was read off by a second observer, and written down 

 on paper by a third ; a fourth observer read off the indications of the dynamome- 

 ter at the same instant, and they were registered opposite to the instant of time 

 to which their observation corresponded ; and, for the sake of accuracy, two copies 

 of this register were kept. The indications of this register form the body of ex- 

 periments of 1835. 



The experunents of 1835 were conducted on the following vessels : — 



The Wave, . . No. I. 

 The Dirleton, . No. II. 

 The Raith, . . No. III. 

 The Houston, . No. IV. 

 The first of these having been made the subject of experiment at seven different 



VOL, XIV. PART I. N 



