VOL. LXVIII.] PHILOSOPHICAL TRANSACTIONS. 427 



and Its continuance in the air is of so short duration, that even in the dryest, 

 warmest weather, little is to be apprehended from the too great rigidity of the 

 wings. In my opinion, though this circumstance of moistening them may be 

 of some use, and a secondary advantage, yet they seem to touch the water for a 

 more important purpose, for the same reason that a diver or swimmer, when 

 below the surface of another element, is very frequently obliged to emerge into 

 his own. It may also be of some use in giving the animal new force and vigour 

 for another departure. 



But as flying is only a sudden expedient, in order to escape the jaws of their 

 enemies, and by no means their natural or usual mode of existence, there seems 

 not to be any particular or remarkable apparatus necessary for a long subsistence, 

 nothing is wanted but the power of motion in our atmosphere, and the drying 

 of their wings appears to be the only inconvenience they are likely to suffer. 

 Hence it is, that in every other part of their frame and structure, small provi- 

 sion is made by all-bountiful nature for this transmigration. In flying, not only 

 their fins and wings are much expanded, but also their tail ; they skim along the 

 surface of the deep with great velocity, somewhat in the manner of a swallow, 

 but in straight lines, and from the blackness of their backs, the whiteness of 

 their bellies, and forked expanded tails, they have much the same appearance.* 

 They can fly 50, 6o, or more yards at one stretch, and repeat it a 2il or even a 

 3d time, only the slightest momentary touch of the surface that can be con- 

 ceived intervening. 



They are seldom solitary, but rise in flocks or shoals.-|- In taste they some- 

 what resemble a mackerel. They are driven out of their own element by the 

 shark, the porpoise, the albicore, the bineto, and dolphin, to become a prey in 

 ours to the booby, the man of war, and tropic bird ; but I suspect their vision 

 in air is not very distinct, as they often in their flight fall a ship-board, or strike 

 against whatever happens to be in their way, as was the case with all these I 

 examined : and indeed the form of the crystalline humour of the eye seems to 

 countenance this opinion, being of the same spherical figure with that 

 of the greatest part of those fishes that altogether inhabit the watery element. 



XXXF^II. Experiments on Electricity, being an Attempt to shew the Advantage 

 of Elevated Pointed Conductors. By Mr. Edward Nairne , F. R. S. p. 823. 

 A difference of opinion prevailed some time ago, and has of late been revived, 



* Since writing the above, I find the ancients were acquainted with this species ; Phny mentions it 

 under the name of the Hirundo. — Orig. 



f We found them in greatest quantities between tlie latitude of 1 J' and 10° north, from 20° to 

 30- west of die meridian of London ; but they abound between tlie Tropics in many other places of 

 the vast Atlantic, as well as in the Indian Ocean. — Orig, 



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