Royal Institution. 381 



sum of those in the twelve hours of the night at St. Helena, and 

 about 2*6 times as great at the Cape of Good Hope; while at Ho- 

 barton the sum of the twelve night ratios slightlj^ exceeded the day ; 

 at Toronto the excess was larger, viz. as 1*3 to 1. The laws of 

 easterly and westerly disturbances, in relation to the local hours, are 

 then examined separately. At St. Helena and the Cape, the easterly 

 day- disturbances exceed the easterly night- disturbances, and the 

 westerly day-disturbances exceed the westerly night- disturbances. 

 These results are compared with those at Toronto and Hobarton. 



At St. Helena, although but comparatively few disturbances occur 

 during the night hours, those disturbances are almost all westerly 

 (183 disturbances, in all, occurred in nine night hours during five 

 years, of which 174 were westerly and but nine easterly). In the 

 day hours the westerly only slightly exceed the easterly disturbances. 

 At the Cape, the westerly excess is less in the night and greater in 

 the day than at St. Helena, and the night excess much greater than 

 the day excess. 



At St. Helena, the fact of the disturbances being more frequent in 

 the day than in the night is consistent in every month of the year ; 

 this appears worthy of remark when it is remembered that at St. 

 Helena the curve of the diurnal variation of the declination is pre- 

 cisely reversed at two opposite periods of the year ; in one case cor- 

 responding to the curve of diurnal variation in middle northern lati- 

 tudes, and in the other to that in middle southern latitudes. 



The mean effect of the disturbances which have been separated 

 as described, and which comprise all of largest magnitude, is a con- 

 stant westerly effect at every hour both at St. Helena and the Cape 

 of Good Hope, acting more energetically in the night than in the 

 day. At Toronto the mean effect is westerly in the day and easterly 

 in the night ; at Hobarton, easterly in the day and westerly in the 

 night. 



ROYAL INSTITUTION OF GREAT BRITAIN. 



Jan. 28, 1853. — " On Gerhardt's discovery of Anhydrous Organic 

 Acids," by Professor Williamson. 



The discovery by M. Gerhardt of a number of anhydrous organic 

 acids has thrown so much light on one of the most important ques- 

 tions of chemical philosophy, that it constitutes one of the most 

 remarkable illustrations of the manner in which the rich materials 

 of organic chemistry may be brought to bear on the explanation of 

 the pheenomena of chemical action and the laws of chemical com- 

 binaiion. 



It is not unworthy of remark, that the bodies prepared by Ger- 

 hardt had for some years past been supposed to exist ready formed 

 in combination with water and other bases, and that the chief ob- 

 jection to that supposition was founded on the circumstance of their 

 never having been separated from such combination, and presented 

 in an isolated form. In fact, Gerhardt has supplied the very link 

 in the chain, which was expected to constitute evidence for a fami- 

 liar theory of the constitution of salts. But the process by which 



