10 l-HILOSOPHICAL TRANSACTIONS. [aNNO 1703. 



That ] might yet more fully satisfy myself, I caused some of these weeds to 

 be taken out of a ditch, which was full of these weeds; but the largest of them 

 were much smaller than the beforementioned, though their leaves were much 

 thicker. Having examined them, I found, that although they were arrived to 

 their full growth, they had but two roots, which were longer than the roots of 

 the first weed ; and when I viewed the smaller weeds, I could perceive they had 

 a great many, but very short roots. While observing the last weed, I saw a 

 great number of animalcula swimming in circles through the water, and so 

 thick together, that even to the naked eye they seemed like a cloud; I never 

 saw any of these animalcula in other waters ; and the next day they were all 

 gone. There was a great many sorts of these animalcula, and each had their 

 different motion, and all so small as to escape the naked eyes. Among these, 

 I observed some which were much larger than the rest, and were coupled to- 

 gether, in which action they lay very still on the sides of the glass, till a larger 

 sort interrupted them ; while they were quiet, I could easily see those parts 

 which they use in motion, and also the nootion of several parts of their body. 

 These animalcula were so large, that the eye might see them in clear water, 

 and in a glass tube; among several of these sorts I could perceive some as large 

 as little sands, and as completely formed as garden spiders. 



jin Account of Books. I . Astronomic^ Phystcce et Geometricis Elementa. Auc- 

 tore Davide Gregorio, M. D. Astronomiie Prqfessore Saviliano et R. S. S. 

 Oxonue, 1702, /o/.* N° 283, p. 1312. 



What the world has hitherto wanted, the learned Dr. Gregory has supplied, 

 in a complete system of true and physical astronomy ; and as the last ages 

 have been sufficiently furnished by the ancients, with the elements of geome- 

 try, so doubtless the future will have recourse to this book, for those of physi- 

 cal and geometrical astronomy. 



The physical explications are all built on the principles of the great Newton ; 

 and he has, throughout the whole work, so mixed these with the phaenomena 

 themselves, that they who are solicitous about the astronomical part only, may 

 understand it, as it is there delivered, without inquiring into the physical causes. 

 The geometrical parts are either all proved from the citations of standard 

 authors, or demonstrated in lemmas, inserted in their respective places. And 

 that the reader may not think physical inquisitions in astronomy to be only 

 new, in his preface he proves from Diogenes Laertius, Plutarch, Stobaeus, &c. 



•> • This excellent account of Dr. Gregory's astronomy, and other curious astronomica! raatteri, 

 nai rauch the appearance of the style and compositiou of the learned Dr. Halley. 



