[_And wide in ocean_. l. 164. Denser bodies propagate vibration or sound better than rarer ones; if two stones be struck together under the water, they may be heard a mile or two by any one whose head is immersed at that distance, according to an experiment of Dr. Franklin. If the ear be applied to one end of a long beam of timber, the stroke of a pin at the other end becomes sensible; if a poker be suspended in the middle of a garter, each end of which is pressed against the ear, the least percussions on the poker give great sounds. And I am informed by laying the ear on the ground the tread of a horse may be discerned at a great distance in the night. The organs of hearing belonging to fish are for this reason much less complicated than of quadrupeds, as the fluid they are immersed in so much better conveys its vibrations. And it is probable that some shell-fish which have twisted shells like the cochlea and semicircular canals of the ears of men and quadrupeds may have no appropriated organ for perceiving the vibrations of the element they live in, but may by their spiral form be in a manner all ear.] 165 V. "SYLPHS! YOU, retiring to sequester'd bowers, Where oft your PRIESTLEY woos your airy powers, On noiseless step or quivering pinion glide, As sits the Sage with Science by his side; To his charm'd eye in gay undress appear, 170 Or pour your secrets on his raptured ear. How nitrous Gas from iron ingots driven Drinks with red lips the purest breath of heaven; How, while Conferva from its tender hair Gives in bright bubbles empyrean air; 175 The crystal floods phlogistic ores calcine, And the pure ETHER marries with the MINE. [_Where oft your Priestley_. l. 166. The fame of Dr. Priestley is known in every part of the earth where science has penetrated. His various discoveries respecting the analysis of the atmosphere, and the production of variety of new airs or gasses, can only be clearly understood by reading his Experiments on Airs, (3 vols. octavo, Johnson, London.) the following are amongst his many discoveries. 1. The discovery of nitrous and dephlogisticated airs. 2. The exhibition of the acids and alkalies in the form of air. 3. Ascertaining the purity of respirable air by nitrous air. 4. The restoration of vitiated air by vegetation. 5. The influence of light to enable vegetables to yield pure air. 6. The conversion by means of light of animal and vegetable substances, that would otherwise become putrid and offensive, into nourishment of vegetables. 7. The use of respiration by the blood parting with phlogiston, and imbibing dephlogisticated air.