228 Cambridge Philosophical Society. 



cates that the correction for temperature of this particular aneroid 

 was nearly of the same amount as that of the mercurial barometer, 

 even supposing it to be free of index-error. In the second table of 

 Mr. Dent, the readings of a maximum and minimum thermometer 

 are given, neither of which were probably true at the time the ob- 

 servation was taken. 



The sympiesometer is fully described, an instrument that is not 

 used in meteorological investigations ; whilst the dry and wet bulb 

 thermometers are not described at all, which are in use in every ob- 

 servatory. 



The rain-gauge figured in the book is one with a float and staff, 

 of the worst possible form ; and if made as sketched in the book, 

 would give erroneous results, particularly when the wide staff was 

 high, and thereby increasing to- a considerable extent the receiving 

 surface of the gauge. 



No mention whatever is made about the necessity of having good 

 instruments, and such that have been compared with standards before 

 use. No instructions are given as to the making of observations, or of 

 the method of recording them ; and yet in any work bearing the title 

 of an Introduction to Meteorology, these ought surely to be given, 

 and particularly when one chapter is devoted to instruments. The 

 work should more properly be called, a Treatise upon Meteorological 

 Phsenomena ; and even in this particular it is incomplete. Although 

 a multitude of facts are collected and detailed, and some of a recent 

 date, no mention whatever has been made of the fine series of 

 results derived from the Makerstoun observations by Sir Thomas 

 Brisbane, and published in the Transactions of the Royal Society of 

 Edinburgh ; neither of any of the meteorological papers of results 

 published in the Philosophical Transactions for several years past ; 

 and the references to the Greenwich volumes are very few, and none 

 since the volume for 1844. 



We shall conclude with one remark only. Dr. Thompson in his 

 concluding paragraph says, that the instruments of which he has 

 spoken are the chief instruments used by meteorologists. In our 

 most active meteorological observatories not half the instruments here 

 described are used at all ; and the instruments actually required are 

 few in number : these should be good ; and before use, should pass 

 through the hands of a gentleman accustomed to them. In fact the 

 general laws which govern atmospheric phsenomena can be found 

 only by accurate deductions from the observations of such instru- 

 ments. 



XXX. Proceedings of Learned Societies. 



CAMBRIDGE PHILOSOPHICAL SOCIETY. 

 [Continued from vol. xxxiv. p. 458.] 

 April 23, ^^N the Variation of Gravity at the Surface of the 

 1849. ^ Earth. By G. G. Stokes, M.A., Fellow of Pem- 

 broke College, Cambridge. 



In the theory of the figure of the earth on the hypothesis of ori- 



