o?i the Velocity of Sound at Port Bowen. 13 



a climate we should not have recorded more particularly the 

 several circumstances which are required in such experiments. 

 It does not appear, however, that we have neglected any cir- 

 cumstance which he has pointed out as necessary, except die 

 precise velocity of the wind, — for which purpose unfortunately 

 we had no anemometer : nevertheless the velocity of the wind 

 during our experiments must, we conceive, be of little impor- 

 tance ; as in all cases, save two, the observations were made 

 in calm weather, or when very light airs prevailed, as stated 

 in the table. With respect to " the angle between the di- 

 rection of the sound and that of the wind," we beg to ob- 

 serve that, as the exact bearing of the gun is given, and like- 

 wise the direction of the wind to the nearest point, we do not 

 comprehend what reason Mr. Galbraith has for regretting 

 that " the direction of the wind relative to that of the sound 

 was not ascertained." 



The circumstance of our not having noted the state of the 

 hygrometer, cannot properly be considered an omission, since 

 its indications were always those of perfect dryness in very 

 low temperatures, as stated in the body of the narrative. 



It is not therefore to the omission of the velocity of the 

 wind, that the want of coincidence between Mr. Galbraith's 

 theoretical deductions, and our practical results, is to be attri- 

 buted ; nor is the mistake we have fallen into ascribable to 

 the same cause, but solely from our having inadvertently 

 spoken of an increased density, where we ought to have said 

 a diminished elasticity. At the same time we think Mr. Gal- 

 braith has by no means fairly stated our remark, having 

 omitted that part which applies to temperature : for we did 

 not speak of the increased density of the atmosphere, uncon- 

 nected with temperature; whereas, as Mr. Galbraith has 

 quoted our remark, it appears that density as measured by the 

 barometer alone was contemplated. However, Mr. Galbraith 

 will perhaps do us the justice to beheve, that it was certainly 

 far from our intention to oppose our opinions on these points 

 to those of Newton or Laplace. We considered our remark 

 at the time, as a fair deduction from our own experiments, 

 without at all considering with what theory it might be at va- 

 riance : our only wish being, to furnish data for philosophers 

 to arrive at such laws as will make the comj)uted and observed 

 velocities of sound agree more exactly with each other, than 

 appears to be the case, in the present state of our information 

 of all the modifyhig circumstances to which the motion of 

 sound is subjected. We are, Sir, yours, &c. 



Will. Enw. Parry, Capt. ) .. ^^ 

 Henry Foster, Lieut. J ' ' 

 IV. Ex- 



