Scientific Intelligence. Meteorology. 191 



travellers do not depend solely on the diminution of the pres- 

 sure on the surface of the body, and on the rarification of 

 the air interfering with the perfect accomplishment of the act 

 of respiration, but are likewise caused by fatigue, by the ef- 

 fects of cold, and even by the apprehension of the danger with 

 which these excursions are almost always accompanied. The 

 effects resulting from the augmentation of atmospheric pressure 

 may, in like manner, be complicated by the effects resulting 

 from accessory circumstances. Thus, formerly we referred al- 

 most exclusively to this cause the symptoms experienced by 

 workers in the diving bell, whilst a portion of the resulting ac- 

 cidents was owing to commencing asphyxia ; and they have 

 ceased to manifest themselves since means have been devised to 

 renovate the air which is vitiated by respiration. It is, more- 

 over, true respecting the augmentation of the pressure, or of 

 its diminution, that its influence varies in different individuals, 

 in some it is scarcely marked, whilst in others it will produce 

 swooning. In general, this sensibility to change of atmosphe- 

 ric pressure most strongly exhibits itself in persons of a feeble 

 constitution, of great nervous excitability, in those whose respi- 

 ration is not quite healthy, or who are the victims of rheuma- 

 tism, or have suffered from bad wounds. In some we observe 

 a state of discomfort, or of pain more or less acute, appear un- 

 der the influence of the different causes which act upon the 

 barometer, the hygrometer, or the electrometer ; and these in* 

 dications, like those of the instruments we have just named, 

 mark beforehand the occurrence of certain meteorological 

 changes. It is these individuals that M. d'Hombres Firmas 

 regards as living barmometers. 



7. Luminous Appearance at Sea off the Shetland Isles. 

 A curious luminous appearance at sea is mentioned in the fol- 

 lowing abstract from a letter to Robert Stevenson, Esq. En- 

 gineer, by the Light-house Keeper on Sumburgh Head in Shet- 

 land : " Monday, September 19. 1836 Sumburgh Head 

 Light -house The herring-boats went out through the night 

 there came on a severe gale of wind from the north-east, which 

 drove them from their nets, and scarcely any one of them got 

 into their own harbours. Mr Hay's fishermen lost 180 nets, 

 Mr Bruce of Whalsey lost 114 nets, and a great many of the 

 poor men lost the whole of their nets. The fishermen also in- 



