VOL. XVII.] PHILOSOPHICAL TRANSACTIONS. 565 



azimuth of the greater star is taken, by a inicrometer consisting of several fine 

 threads parallel and transverse, may at the same time be observed the distance of 

 the two stars from each other, in that position, both being at once within the 

 reach of the micrometer; which distance, the instrument remaining unmoved, 

 if it be found at different times of the year not to be the same, will prove that 

 there is a different parallax of these two stars. 



This latter part of the observation, viz. of their different distances at different 

 times, I suggest as more easily practicable, though not so nice as the former : 

 for it may be done, I think, without any further apparatus there than a good 

 telescope of ordinary form, furnished with a micrometer, carefully kept un- 

 varied during the interval of the observations. And if this part only of the 

 observation, without the other, be pursued, it matters not though the two ob- 

 servations near the two solstices be, one at the eastern, the other at the western 

 azimuth, whereby both may be taken in the night-time ; for the distance must 

 at both azimuths be the same. If, after observing the azimuth of the greater 

 star, it be necessary to move the micrometer for measuring its distance from 

 Alcor, that may be done another night, and it is not necessary to be done at 

 one observation, for that distance cannot be discernibly varied in a night 

 or two. 



An Account of a Booh : viz. — Synopsis Methodica Animalium Quadrupedum, et 

 Serpentini Generis, Auth. Joanne Raio, S. R. S. N" 202, p. 849. 



The design of this present work, is to reduce all quadrupeds into the most 

 proper and natural method, for the more easily comprehending and remember- 

 ing them ; and to add to the several species short characteristic notes, by which 

 they may be distinguished from others of the same kind. 



First of all, there is proposed the most exact division of all animals in gene- 

 ral, which is first into sanguineous and exsanguineous. Under the exsanguineous, 

 or such as want that red liquor we call blood, are comprehended, 1 . All crusta- 

 ceous fishes, crabs, lobsters, shrimps. 2. All testaceous or shell fishes, as 

 cockles, muscles, oysters, scallops, periwinkles, whilks, &c. as also all land 

 shell-snails. 3. Those called moUia, or soft-fishes, as pulps, cuttle-fishes, 

 naked snails, &c. 4. Insects of all sorts. 



The sanguineous kind are divided into such as breathe by lungs, and such as 

 breathe by gills, of which kind are all sanguineous fishes, except the whale- 

 kind. Such as breathe by lungs are divided into those that have but one ven- 

 tricle in the heart, and such as have two ventricles. Of the former kind, are 

 those called oviparous quadrupeds and serpents. 



The latter are again subdivided into viviparous, or such as bring forth 



