Prof. Guthrie on Drops. 



[Recess, 



ble in the S. photograph not seen in mine, which may be accounted for from 

 our different positions in respect to the central Hne of the ecUpse. 



Between I and K, at a distance from I equal to about two-thirds the 

 angular interval, there is in the S. photograph a prominence consisting of 

 two round dots, which extend beyond the moon's limb to precisely the 

 same extent as the prominence K protrudes in Professor Secchi's photo- 

 graph beyond the moon's limb in excess of what it does in my own. 



The prominence K has precisely the same form in every respect in the S. 

 photograph as in mine, so far as mine shows it ; but on account of parallax, 

 more of it is seen in the S. photograph than in mine. 



Beyond K is another prominence, visible in the S. photograph about 17° 

 distant from K, a small round prominence which could not have been 

 visible from my station. 



Of the remaining prominences, L, M, N, O, P, Q, R, none were visible at 

 the epoch of the photograph. 



In conclusion, the photographic images of the prominences, so far as they 

 are common to the two photographs taken at Miranda and Desierto de las 

 Palmas, accord in their most minute details. The photographs must, from 

 the difference of position of the two stations, have been made at an abso- 

 lute interval of about seven minutes ; and this fact, while it strongly sup- 

 ports the conclusion that the protuberances belong to the sun, at the same 

 time shows that there is no change in their form during an interval much 

 greater than the whole duration of an eclipse. 



II. On Drops." By Frederick Guthrie, Esq., Professor of Che- 

 mistry and Physics at the Royal College, Mauritius. Communi- 

 cated by Professor Stokes, Sec. R.S. Received July 15, 1864. 



In the following investigation, the word drop is used in a rather more 

 definite sense than that which is usually attached to it. 



In common speech a drop signifies any mass of liquid matter whose form 

 is visibly influenced towards the spherical by the attraction of its parts, and 

 whose sensible motion or tendency is towards the earth. This definition 

 both includes drops with which we are not here concerned, and excludes 

 others which we shall have to consider ; for we shall] have to measure the 

 size of drops ; and it can only be of aVail to measure the size of such drops 

 as are formed under fixed and determinable conditions. 



How many drops, according to the usual scope of the term, are formed 

 under indefinite conditions. For instance, a rain-drop depends for its size 

 upon such circumstances as the quantity of vapour at the time and place 

 of its formation, the tranquillity and electrical condition of the air, its rate 

 of motion, the number and size of the drops it meets with in its course, 

 &c., all of which are fortuitous, or, at least, immeasurable conditions. 



With such drops we have here nothing to do, but only with those 

 which are formed under fixed circumstances. On the other hand, we 



