238 PHILOSOPHICAL TRANSACTIONS. [aNNO 1685. 



with the /^B C A ; so in the triangle E F D, the Z.E, with the sides, E D, D F 

 being known, E F will be found, with the /^ E D F. Lastly, in the triangle 

 A C D, the Z. A C D (= B C D - B C A), with its legs A C, C D, being known 

 the side A D will be known ; and in like manner E C, in the triangle E D C. 



Note that, in this problem, as also in the first and second, if the two stations 

 fall in a right line with either of the given objects: the locus of A or E being 

 a circle, the particular point of A or E cannot be determined from the things 

 given. As to the other cases of this third problem, wherein A and E may shift 

 places, i. e. only D, F, E, may be visible at A, and only A, B, C, at E; or where- 

 in B, D, E, may be visible at A, and only C, F, A, at E ; or wherein A may be 

 on one side of the quadrilateral, and E on the other ; or one of the stations 

 within the quadrilateral, and the other without it ; for brevity's sake these may 

 be here omitted, as the surveyor will easily direct himself in those cases, by 

 what has been said above. The solution of this third problem is general, and 

 serves also for both the preceding ones. For suppose C, D the same point in 

 the last figure, and it gives the solution of the second problem: but if H, C, be 

 supposed the same points with D, F, by proceeding as in the last, you may 

 directly solve the first problem. 



On the Circulation* of the blood, as seen by the help of a Microscope, in the 

 Lacerta Aquatica. By JVm. Molyneux, Esq. N" 177, p. 1236. 



Dublin, Oct. 27, l685. — Our Society lately received transcripts of two of 

 Dr. Garden's letters, the first dated from Aberdeen, July 17, l685, to Dr. 

 Middleton; the other Sep. 4, 1()85, to Dr. Plot. To both these letters I have 

 something to say. 



In the first he gives an account of the visible circulation of the blood in the 

 water-neut, or lacerta aquatica; and I am heartily glad, that this learned and 

 ingenious doctor has hit upon this experiment. It is now above two years and 

 a half since I first discovered this surprising appearance, and wrote a large ac- 

 count of it. May 12, l683, as also of the whole anatomy of this animal, to 

 my brother, who was then at Leyden. And I have since that showed it fre- 

 quently, both on the outside without dissection, and in the inward vessels also, 

 to several curious physicians and philosophers, to their great satisfaction and 

 admiration; particularly I exposed it first to our Society, May 26, l684, as 

 appears by the following minute taken from our registry. " May 26, 1684, 

 Mr. Molineux opened before the company a water-neut, which he takes to be 

 the salamander or lacerta aquatica; in the body of this animal there are two 

 long sacculi aerei, on which the blood vessels are curiously ramified; to these 

 blood vessels applying a miscroscope, he showed the circulation of the blood ad 



