VOL. v.] PHILOSOPHICAL TRANSACTIONS. 435 



time change its situation ; as rivers cannot remain long without winding -and 

 changing their course, if it happen that the ground over which they run be 

 unequal, or of a different nature. 



If this should be the case, there would be no hopes of finding a regular hypo- 

 thesis for that change, forasmuch as it would depend on causes that have no 

 regularity at all in them, as most of the mutations of nature are. 



From this observation mathematicians are invited from time to time to make 

 the like in their countries, to see whether in this change there be any regula- 

 rity. If it had been observed every year, we should already know the progress 

 thereof, and see whether there were an uniformity, and in what time the needle 

 did exactly respect the pole. Wherefore it were very desirable that for the fu- 

 ture they would use greater care and diligence in making most exact meridians, 

 as well for their own observations, as for the conveniency of those who in their 

 travels shall have the curiosity of observing with the needle itself, as M. Auzout 

 designed to do in the cities where he passed, if he had found meridians there, 

 or such as had been unsuspected of the proximity of iron. 



It were well to observe, whether the declination which almost through all 

 Europe has been eastward, be now every where westward ; as also, whether in 

 America, where the declination was almost every where westward, it be increased 

 or no proportionably ; and so of other parts of the world. 



So far this relation, in pursuance of which, order has been given by the Royal 

 Society, that precise meridians be made in several places of England, for ob- 

 serving the present declination of the needle from them here in London, and 

 other cities of this kingdom ; and that even those meridians that were made 

 very exactly many years ago be examined by a careful describing of new ones, 

 to see whether they still hold true, in regard of the suspected alterations in 

 nature. 



If any shall inquire after the manner of finding the variation of the needle, he 

 will find several ways of doing it accurately, both by sea and land, in N° 24 of 

 these Tracts ; where also the great usefulness of making exact observ^ations of 

 this kind is taken notice of, both for the discovery of the true cause of the 

 magnet's verticity, and for the finding the longitude at sea. 



Extract of a Letter, dated Venice, Jan. 25, I6j0, from Sig. Jacomo 

 Grandi, concerning some Anatomical Observations, and two odd 

 Births. Translated by Mr. Oldenburg. N" oS, p. 1188. 



In my anatomical dissections at Venice, the first year, I met with nothing 

 curious, but the virsungian channel manifestly inserting itself in the spleen, and 



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