282 LIGHT SCIENCE FOR LEISURE HOURS. 



however, from variations of flexure. It presents, indeed, 

 six well-marked convexities, and as many concavities ; 

 in other words, no less than twelve points of inflexion. 

 The most remarkable irregularity of this sort is that 

 exhibited near the end of November ; and it is note- 

 worthy that this irregularity is presented by continental 

 climate-curves also. It has been ascribed by Ertel to 

 the effect of the meteor-zone which causes the 

 November shower. But as it is exhibited by the curves 

 of horary as well as of diurnal means, while the 

 meteor-zone cannot by any possibility affect the tem- 

 perature of the earth's following hemisphere, and as, 

 further, it does not correspond to the true date of the 

 shower, this view may be looked upon as doubtful. 

 The August curve occurring near the maximum 

 elevation where slow change was to be expected, is 

 also well worthy of notice ; as are the January and 

 May flexures. 



It will be noticed that nothing has been said of 

 extreme heat or cold occasionally experienced in 

 England. As such visits generally last but for a short 

 time, their effects are not very injurious, save on the 

 very weak, the aged, or the invalid. Corresponding to 

 the passage of an immense heat-wave or cold-wave, 

 there invariably occurs a sudden rise in the mortality- 

 returns ; but almost as invariably the rise is followed 

 by a nearly equivalent, but less sudden fall ; showing 

 conclusively that many of the deaths which marked the 

 epoch of severest weather occurred a few weeks only 

 before their natural time. 



