628 PHILOSOPHICAL TBANSACTIONS. [aNNO 1742-3. 



has always been, to compare observations made in countries at a vast distance 

 from each other. But he here considers whether the same end may not be ob- 

 tained in the same country, or without change of place. 



To this end, he first relates what the learned Huygens has laid down, in his 

 " Dissertation on the Cause of Gravity," when he endeavoured to discover, 

 how much a pendulum ought to be shortened, which is carried from France to 

 the equator. And then he states his own contrivance. But Huygens's con- 

 trivance need not be repeated here, as it can be seen in his book. Nor does 

 it seem proper to detail the particulars of Sig. Poleni's construction, as nothing 

 has ever resulted from it, and as the matter has been long since settled, as to 

 the variation in the length of pendulums depending on the cause in question. 



Observaliones Astronomies habitie in Collegio Pekinensi a Patribus Societatis 

 Jesu, a Mense JSovembri 1 740, a Do. Jacobo Hodgson, R. S. S. cum Regia 

 Societate communicatee. N° 468, p. 306. 



These Chinese observations are of no use now. 



Account, by John Van Rixtel, F. R. S. of Mr. W. Kerssebooms * Second and 

 Third Treatise, corifirming the Manner how to know the probable Quantity of 

 People in the Provinces of Holland and IVest-Friezland, besides a Foundation 

 on which to prove the probable Lives of Widows, and likewise a Rule to know 

 the Duration of Marriages. N° 468, p. 315. 



Mr. Kersseboom having advanced in his first Treatise, printed anno 1 738, 

 that the provinces of Holland and West-Friezland contained 980,000 souls, of 

 all ages, on a well-grounded supposition, that annually are born in the said 

 two provinces 28000 children alive ; but it having been the opinion, that this 

 should be more clearly demonstrated, he has thought it necessary to comply 

 with the same. In order to which, the author has divided the provinces into 3 

 general divisions, distinguished with the letters a, b, c ; and supposes on good 

 grounds, that in the first division marked a, are born alive annually SSQO chil- 

 dren, B ditto 19070, and c ditto 5040, making all together annually 28000. 

 children. 



And, as it has been proved in his first treatise, that for every child that is 

 born, the whole number of people is 35 times as many ; so it will prove, that 

 these numbers being multiplied together, it renders 980,000 souls. 



But as it was impossible for the author to get an exact account, from all 

 places, of the births, weddings, and burials, (from which last two the first is 



• See an account of the first part. Philosophical Transactions, N" 450. — Orig. 



