tridactylus, and in some measure also the didactylus, has a similar distribution of these arteries.
This peculiar disposition of the arteries in the limbs of these slow-moving quadrupeds, it is thought cannot but retard the velocity of the blood passing into the muscles of the limbs. Whence the well known sluggishness of the animals, to whom this configuration seems as yet peculiar, will perhaps be ultimately accounted for. Something similar has been observed in the carotid artery of the lion, which it is thought may be subservient to the long continued exertion of the muscl of his jaws, in holding a powerful animal for a length of time; and lastly, it is conjectured that the ruminating animals have a somewhat similar aplexus of arteries in the neck, which operates in retarding the velocity of the‘ fluids in those parts.
We are here presented with a numerous set of experiments and observations, which the author does not deliver as a series calculated to elucidate any particular object, but rather as the results of the first steps of an investigation; which being of considerable magnitude, and not to be accomplished in a short period of time, are here brought forward in a detached form, in order to preserve them from oblivion, should any unforeseen circumstances prevent his continuing the pursuit. They are classed under sixteen different heads, of which the following are the titles, and some of the principal inductions.
1. Of the Quantity of Air discharged through an Aperture—This was deduced from the quantity of pressure of water, on a body of air rushing through a small aperture at the end of a tube. The result was, that the quantity of air discharged by a given aperture is nearly in the subduplicate ratio of the pressure ; and that the ratio of the expenditures by different apertures, with the same pressure, lies between the ratio of their diameters, and that of their areas.
2. Of the Direction and Velocity _of a Stream of Air.—-These were determined by the stream, produced by a known pressure, being made to impinge, in a perpendicular direction, against a white plate, on which a scale of equal parts was delineated, and which was thinly covered with a coloured liquid. The results were here inferred from the breadth of the surface of the plate laid bare by the stream.—The experiments being repeated at different distances between the orifice and the plate. the longitudinal form of the stream could be hence deduced, their sections being bounded by curves, the nature of which could be determined by their ordinates and abscissae. The numerous results obtained in this manner are entered in various tables, and likewise illustrated by figures, in which the longitudinal and not the transverse sections are exhibited to the eye.
3. Ocular Evidence of the Nature of Sound—This is produced by
