VOL. I.] PHILOSOPHICAL TRANSACTIONS. 14J 



13. Whether the operation may be successfully practised, in case the injected 

 blood be that of an animal of another species, as of a calf into a dog, &c. and 

 of a cold animal, as of a fish, or frog, or tortoise, into the vessels of a hot ani- 

 mal, and vice versa ? 



14. Whether the colour of the hair or feathers of the recipient animal, by 

 the frequent repeating of this operation, will be changed into that of the 

 emittent ? 



15. Whether, by frequently transfusing into the same dog the blood of some 

 animal of another species, something further, and more tending to some de- 

 grees of a change of species, may be effected, at least in animals near of kin? 

 (as spaniels and setting dogs, Irish grey-hounds and ordinary grey-hounds, &c.) 



16. Whether the transfusion may be practised upon pregnant bitches, at 

 least at certain times of their pregnancy ? and what effect it will have upon the 

 whelps ? * 



A Method of ohserving Eclipses of the Moon. By Mr. Rook, late 

 Gresham Professor of Geometry. N 22, p. 388. 



Eclipses of the moon are observed for two principal ends: one astronomical, 

 that by comparing observations with calculations, the theory of the moon's mo- 

 tion may be perfected, and its tables reformed ; the other geographical, that 

 by comparing among themselves the observations of the same ecliptic phases, 

 made in divers places, the differences of meridians or longitudes of those places 

 may be discovered. 



The knowledge of the eclipse's quantity and duration, the shadows, curvity, 

 and inclination, &c. conduce only to the former of these ends. The exact 

 time of the beginning, middle, and end of eclipses, as also in total ones the 

 beginning and end of total darkness, is useful for both of them. 



But because in observations made by the naked eye, these times considerably 

 differ from those with a telescope ; and because the beginning of eclipses and 

 the end of total darkness are scarce to be observed exactly, even with glasses 

 (none being able clearly to distinguish between the true shadow and penumbra, 

 unless he has seen, for some time before, the line separating them pass along 

 upon the surface of the moon): and lastly, because in small partial eclipsesj 

 the beginning and end, and in total ones of short continuance in the shadow, 

 the beginning and end of total darkness are unfit for nice observations, by rea- 

 son of the slow change of appearances, occasioned by the oblique motion of the 

 shadow. For these reasons I shall propound a method peculiarly designed for 

 the accomplishment of the geographical end in observing lunar eclipses, free, as 

 far as is possible, from all such inconveniences. 



* To most of these questions a negative answer may be given. 

 VOL. r. T 



