166 Mr J. D. FORBES on the Horary Oscillations 



results have sometimes been much misunderstood, and spoken of 

 as if they stood in opposition to each other. Mr DANIELL (who 

 is almost the only English writer by whom this subject has been 

 considered at any length), treats the question as one of quality 

 not of degree. The atmospheric tide is much smaller in Europe, 

 at the level of the sea, than at the same level at the Equator : 

 if, therefore, we consider the influence of height to be equal in 

 both cases, and in the same direction, it is very obvious that 

 while, at the Equator, the oscillation may be only diminished in 

 dimension, at the same height in the Temperate Zone, it may 

 have become null, or changed its sign ; that is, being negative, 

 the time of maximum below will correspond with that of mini- 

 mum above, and vice versa, a phenomenon perfectly in confor- 

 mity with the laws which ordinarily regulate physical causes, and 

 deducible from the abstract consideration of quantity, therefore 

 to be considered in no respect as an anomaly in the quality of 

 the effect, or as a change per saltum in the course of nature. 



9. But, what is very remarkable, a precisely analogous fact has 

 been discovered in Lat. 74, by Captain Sir EDWARD PARRY, 

 whose admirable meteorological registers were a most valuable 

 donation to science. This circumstance had for some years been 

 suspected, from the earlier journals of PARRY and other Arctic 

 voyagers ; but these results were received with just doubt, because 

 the barometric registers wanted the indispensable element of the 

 temperature of the mercury, which, under any circumstances, and 

 especially those of an arctic voyage, might produce, by an average 

 difference of temperature at one hour of the day from that at 

 another, results, erroneous in amount, or even opposed to the 

 truth. For example, it will be seen by the four first tables at- 

 tached to this paper, that in the entire annual results, even in 

 this temperate climate, a constant excess of temperature at 4 p. M. 

 was observed above that at 8 A. M., amounting to a degree and a 

 half of Fahrenheit, which, supposing no oscillation, would give 

 rise to a negative one of between four and five thousandths of an 



