VOL. XVII.] PHILOSOPHICAL TRANSACTIONS. 581 



them, thought it might not be a thing ungrateful to the learned, if he published 

 what his own thoughts might be towards the clearing of the abstruse matters 

 there treated. He proceeds on each chapter, as the author of the theory has 

 written them, in his English copy, first briefly stating the contents, and then 

 offering what he has to say upon them. 



3. Epistola ad Regiam Societatem Londinensem, qua de nuperis Terne-motibus 

 disseritur, et verce eorum Causce eruuntur. Lond. inAto. 1693. N° 203, p. SQS. 



An astrological treatise, asserting that the late dreadful earthquakes, and 

 other convulsions in nature, are owing to the influences of the stars, &c. 



A.T raite des Moyens de rendre les Rivieres navigables, &c. a Paris, 1693, 



in 8vo. N° 203, p. 8g4. 



The author of this treatise says, in the preface, that the methods and 

 machines he proposes, are not mere chimeras, but are already put in practice, 

 chiefly by the Hollanders, who have the most of any cultivated this art. 



The work treats on the various impediments to navigation in rivers ; of their 

 nature, causes, effects, and the means of removing them. 



^n Experiment, made before the Royal Society, on the Effects of the Air on a 

 transparent Liquor, applied to explain Changes of Colour in the Blood of 

 Respiring Animals. By Fr. Slare, M.D. F.R.S. &c. N° 204, p. BQS. 



To make this experiment, put a quantity of fresh filings of copper in a glass 

 phial, of a broad and even bottom, and then pour on them a urinous spirit, 

 either of sal ammoniac, or of urine itself, not made with quick-lime : the glass 

 should not be filled much above half, and then it must presently be so exactly 

 stopped, that no air be admitted; for an error in one circumstance will mar the 

 whole experiment. The foundation of this experiment is justly due to the 

 immortal Mr. Boyle; but I have endeavoured to bring it home to my own pro- 

 fession, to justify a notion of some importance, though much disputed, con- 

 cerning an alteration made by the air on human blood, both as to colour, and 

 other virtues. In making the experiment, you will observe, for 4, 5, or 6 days, 

 the tincture becoming deeper and deeper, and then it will be at a stand for 2 or 

 3 days more or less, and afterwards it will gradually decline, until it become 

 quite pale, and void of all colour. When it is in this state, the easiest way of 

 performing the experiment is to decant this clear spirit into a glass, so as to 

 leave all the filings behind, which will show that the filings did not give this 

 tincture anew, but that it is owing to the influence of the air. But in case you 



