354 Mr. A. Bird on a Water-Barometer \ 



action for two years, but afterwards got out of order. In de- 

 scribing the action, Mr. Daniell states that " the water appears to 

 be in perpetual motion, resembling the slow action of respiration." 



I can fully corroborate Mr. Daniell in this particular, and 

 from careful and continued observation am able to state that the 

 times of the oscillations are about every four minutes and twenty 

 seconds. It is requisite to watch the oscillations with a magni- 

 fier, as they vary from the twentieth to the thirtieth part of an 

 inch, which distance can be well observed when it is slightly 

 magnified. But the most surprising oscillations in the water- 

 barometer are during a thunder-storm accompanied with great 

 falls of hail and heavy rain-drops. I have given a chart of five 

 minutes' readings for one hour and five minutes during a heavy 

 thunder-storm from the north-east, which passed over Birming- 

 ham July 20, 1859. The upper curved line shows the water- 

 oscillations, and the lower curved line shows the oscillations in 

 the mercurial barometer. The temperature is recorded at the 

 foot. It will be observed that while the water-column rose and 

 fell in a most surprising manner, the mercurial column showed 

 hardly any motion, which was of a laggard character. 



At 4.20 p.m. the storm reached its climax, the heavens grew 

 darker overhead, and the water rapidly descended, causing a most 

 impressive feeling on the mind, when suddenly came a terrific 

 blaze of lightning instantly followed by the " thunder can- 

 nonade" (if I may so call it); then down came the hail and 

 heavy rain, and as the sky began to brighten the water com- 

 menced to rise, and in the next five minutes it had risen more 

 than four-tenths of an inch. 



Since Sir John Herschel proposed his new theory — that the 

 disruptive electric discharge is the result, and not the cause of 

 the sudden condensation of cloud into " rain-drops," in conse- 

 quence of the cloud coming in contact with an extremely cold 

 and dry current of air — it has occurred to me that the sudden 

 increase in the density of the air, as shown by the rise of the 

 water-column, may be due to the sudden precipitation of rain- 

 drops of unusual size, leaving the atmosphere drier and conse- 

 quently denser; it being well established that the mercurial 

 column is always high when the air is dry, and vice versa. 



I conclude this account of the water-barometer by stating 

 that the object with which it is written is to give practical direc- 

 tions for its construction with a view to their becoming common 

 for the furtherance of meteorological science. 



I just add that the total cost of the materials need not exceed 

 £3, exclusive of gas-fitter's time. 



I am, &c, 



Birmingham, October 14, 1865. Alfred Bird. 



