Tracts. The Cosmicall qualities of things. [bound with] Observations about the saltiness of the Sea.

First editions, complete; 8vo (17.5 x 12 cm); ownership stamp to front free endpaper recto, pen inscription to verso 'R. Boyle Tractatus V. de rebus naturalibus quibus additum historia qualitatum singularium', closed tear to front free endpaper; [Cosmicall.]: issue without title-ornament, [A]2 cancel-title ([A]3 in Fulton foliation, speculates a cancelled blank), [A]3 advertisement to the reader, [A]4 errata, H7 blank, H8 blank recto, verso label-title, half-titles, pp26-27 of 'Cosmicall Suspitions' misnumbered 22-23, sub-title 'Three Tracts' bound after essay on the 'Temperature of the Subterraneall' (consistent with pagination) and advertisement to rear, 'Subterraneal Regions' C5 recto and verso with identical text, 'Submarine Regions' B2 and B3 cancels; [Observations.] [A]1 blank, A3-A4 recto advertisement to the reader, half-titles, verso advertisements present; bound in contemporary blind-ruled calf, abrasions with loss to leather, joints and covers expertly restored, sprinkled edges, occasional light spotting and minor soiling, very good; [6], 42, [2], 27, [3], 3-28, [6], 3-43, [5], 3-21, [3], 16, [6]; [8], 51, [3], 6, [2], 5, [3], 11,[3], 39, [3], 5, [3], 11, [3], 27, [3], 14pp. A rare sammelband, containing the first editions of two collections of tracts by the natural philosopher and founding fellow of The Royal Society, Robert Boyle (1627-1691). Comprising eight essays in total covering important milestones in the advancement of natural science from observations on astronomy and the voyages of discovery that had taken mankind to new remote regions of the world, to the description of experiments on the problem of rendering seawater fit for human consumption. In particular, Boyle's account of 'local motion' in his essay on Cosmicall qualities made important advances in his corpuscular theory of matter, reaffirming the break he first made with classical Aristotelian notions of the four elements in the Sceptical chymist. Assuming the existence of different 'simple' elements and the occurrence of various combinations of their corpuscles in differing states of 'local motion', Boyle's theory was able to account for the existence of all natural phenomena (Fulton). Also of note are Boyle's descriptions of an 'Engin' invented by a Swedish scientist that had allowed him to remain for several hours at great depths in the sea, and his observations on the change of colour of vegetable extracts when their reaction is changed from acid to alkali. 'One of the important milestones in the history of the theories of chemical combinations' (Fulton). ESTC R3181 & R17503; Fulton 83 & 113.…