Scientific Intelligence — Meteorology. 187 



from the barometrical observations at St Helena, shewing the existence 

 of a lunar atmospheric tide, have been corroborated in the last year by 

 a similar conclusion drawn by Captain Elliot of the Madras Engineers, 

 from the barometrical observations at Singapore. The influence of 

 the moon's attraction on the atmosphere, produces, as might be ex- 

 pected, a somewhat greater effect on the barometer at Singapore, 

 in lat. 1° 19', than at St Helena, in lat. 15° 57'. The barometer 

 at the equator appears to stand on the average about 0,006 in. 

 (more precisely 0,0057, in lat. 1°19'), higher at the moon's culmina- 

 tions than when she is six hours distant from the meridian. 



METEOROLOGY. 



4. Evaporation and Condensation. — The total quantity of dew 

 believed to fall in England is supposed to amount to five inches an- 

 nually. The average fall of rain is about twenty-five inches. Mr 

 Glaisher states the amount of evaporation at Greenwich to have 

 amounted to five feet annually for the past five years, and supposes 

 three feet about the mean evaporation all over the world. On this 

 assumption the quantity of actual moisture, raised in the shape of 

 vapour from the surface of the sea alone, amounts to no less 

 than 60,000 cubic miles annually, or nearly 164 miles per day. 

 According to Mr Laidlay, the evaporation at Calcutta is about 

 fifteen feet annually ; that between the Cape of Good Hope and Cal- 

 cutta averages in October and November, nearly three-quarters of an 

 inch daily ; betwixt 10° and 20° in the Bay of Bengal it was found 

 to exceed an inch daily. Supposing this to be double the average 

 throughout the year, we shall, instead of three, have eighteen feet of 

 evaporation annually ; or were this state of matters to prevail all 

 over the world, an amount of three hundred and sixty thousand cubic 

 miles of water raised in vapour from the ocean alone. — (American 

 Annual of Scientific Discovery , 1853, p. 371.) 



5. The Amount of Oxygen in the World. — . w ' Let us for an in- 

 stant contemplate," says Faraday,* " the enormous amount of oxygen 

 employed in the function alone of respiration, which may be con- 

 sidered in the light of a slow combustion. For the respiration of 

 human beings, it has been calculated that no less than one thousand 

 millions of pounds of oxygen are daily required, and double that 

 quantity for the respiration of animals, whilst the processes of com- 

 bustion and fermentation have been calculated to require one thou- 

 sand millions of pounds more. But at least double the whole pre- 

 ceding quantity, that is to say, twice four thousand millions of pounds 

 of oxygen, have been calculated to be necessary altogether, including 

 the amouut necessary in the accomplishment of the never-ceasing 

 functions of decay. 



As stated in pounds, we can hardly create to ourselves any defi- 



* Faraday's Lectures on the Non-Metallic Elements. 



