X 



456 PHILOSOPHICAL TRANSACTIONS. [aNNO I69I. 



several methods attempted in vain, while the smallness of the angles sought do 

 easily elude the nicest instruments ; but in observing the ingress of Venus into, 

 and egress from, the sun, the space of time between the moments of the in- 

 ternal contacts may be obtained to a second of time, that is, to -ji^ of a second, 

 or 4'" of the observed arch, by means of an ordinary telescope and clock that 

 goes accurately for 6 or 8 hours. 



Some Observations on the Spawn of Frogs, and the Production of Tadpoles. By 

 Richard ffaller, Esq. Reg. S. Secret. N° 193, p. 523. 



About the 12th of March, J 689, I took some frog-spawn out of a ditch, 

 which I suppose might have been spawned about 14 days, and kept it in a galli- 

 pot of water, which I shifted every day or two, and kept them in a window 

 where the sun shone some part of the day. 



At the first they appeared as fig. 5, pi. 1 1, being a round black globule, encom- 

 passed with a clear liquor, and a membrane encompassing that liquor, and that 

 again surrounded with a larger sphere of a more mucous liquor. The 2d and 3d 

 days they appeared as fig. 6; the fourth day as fig. 7. And about the 6th day 

 several of them were loosed from their eggs ; and on the 7th and 8th more of them ; 

 when they appeared of the shape of fig. 8, which in fig. 9> is represented larger 

 than the life, that the position they lay in may be seen the better. On the 7th 

 and 8th days, upon pricking them with the point of a needle, they would con- 

 tract themselves ; and some of them on the 8th day would of themselves bend 

 their bodies, but not move out of their place, which was the bottom of the pot 

 they were kept in. 



When they first got through their egg, which I suppose they did by eating 

 their way, they hung fast to the outside of it, by that part which I afterwards 

 found to be their mouth, and when loosed from their hold, they sunk to the 

 bottom of the water, and could not rise again. On the 9th day they were 

 «iot visibly increased in bulk, only they moved themselves more freely at 

 the bottom of the vessel. At about 14 days end they appeared as fig. 10, at 

 which time they swam about in the water by moving their tails, as fig. 1 1, and 

 some rudiments of their fore legs were visible, which looked forked and like a 

 sprig of a plant. At three weeks end their mouths were to be seen, which 

 they opened and shut, and emitted faeces from the other end. At a month's 

 end the eyes were to be discerned, at which time they would swim near the top 

 of the water, and opening their mouths let out a small bubble of air, and I 

 suppose take in fresh. 



The liquor which was contained in the innermost membrane, was more trans- 

 parent than the other, which was a mucous liquor, and like the white of an 



