4.16 " Mr. Lubbock on the Census. 



torial pendulums represent all the experiments nearly equally 

 well ; but every individual length gives to the earth a different 

 degree of oblateness. 



But if we review the experiments that have already been 

 made on or near the equator, what notion can we have of an 

 ecjuatorial pendulum, which seems to vary irregularly at every 

 different station? The difference in the pendulums observed 

 at Maranham and St. Thomas answers to about nine vibra- 

 tions a-day ; and if we compare the pendulum at Maranham 

 with the experiments at the Isles of France and Guam, the 

 difference amounts to twelve vibrations a-day. To ascertain 

 the exact quantity of such anomalies, and to detect their cause, 

 is assuredly at present the most important and interesting part 

 of this research. Until this be done, the theoretical question 

 can never be placed on a sure foundation. 



May 10, 1830. James Ivory. 



LIX. On the Cen&iis. By J. W. Lubbock, Esq. F.R.S. S'c* 



'T'HE importance of questions connected with the theory of 

 -■- population renders it much to be regretted that we possess 

 so few data for their solution. The bills of mortality are now 

 published (mly in London, Northampton, and a few greattowns, 

 and the parish registers from which these are taken are not, I 

 fear, kept with sufficient accuracy. TheActofthe52ndGeo. III. 

 for the better regulating and preserving parish and other re- 

 gisters of births, baptisms, marriages and burials in England, 

 provides many excellent regulations, but attaches no penalties 

 to the non-performance of them. 



If we refer to the censuses of the population, we find anomalies 

 which it is by no means easy to account for. It seems doubtful 

 whether censuses made at such distant intervals of time as once 

 in ten years can be accurate, as the experience furnished by one 

 must in many cases be lost before a second is commenced. I 

 hope that something may be done to remedy these defects, and 

 to give to these researches an accuracy equal to that which has 

 been attained in almost every other branch of science. 



Two methods present themselves of ascertaining the ratio of 

 the births and the deaths to the population. The first, which 

 is the more obvious, is by comparing the actual numbers of 

 the living, found by any enumeration or census, with that of the 

 births and deaths as deduced from registers of baptisms and 

 burials. 



But these ratios can also be found when the law of mortality 



• Communicated by the Author. 



which 



