OF ARTS AND SCIENCES. 135 



which occasionally afforded signs of being not entirely extinct, and 

 Governor Clinton was inclined to connect them with earthquake move- 

 ments. Professor Mather, who observed the barometer at Copper 

 Harbour during one of these fluctuations, remarks : — ' As a general 

 thing, fluctuations in the barometer accompanied fluctuations in the 

 level of the water ; but sometimes the water-level varied rapidly in 

 the harbour, while no such variations occurred in the barometer at the 

 place of observation.' * 



" As a general rule, these variations in the water-level indicate the 

 approach of a storm, or a disturbed state of the atmosphere. The 

 barometer is not sufficiently sensitive to indicate the sudden elevations 

 and depressions, recurring, as they often do, at intervals of ten or 

 twelve minutes, and the result of observations at such times may be 

 regarded in some degree as negative.! Besides, it may not unfre- 

 quently happen, that, while the effects are witnessed at the place of 

 observation, the cause which produced them may be so far removed 

 as not to influence the barometer. 



" From all the facts, we are led to infer that these phenomena result, 

 not from the prevalence of the winds acting on the water, accumulat- 

 ing it at one point and depressing it at others, but from sudden and 

 local changes in the pressure of the atmosphere, giving rise to a series 

 of barometric waves. The water, conforming to the laws which gov- 

 ern two fluids thus relatively situated, would accumulate where the 

 pressure was the least, and be displaced where it was the greatest. 



" Again, as has been remarked by De la Beche, a sudden impulse 

 given to the particles of water, either by suddenly increased or dimin- 

 ished pressure, would cause a perpendicular rise or fall, in the manner 

 of a wave, beyond the height or depth strictly due to the mere weight 

 itself. The difference in the specific gravity of the water of the lakes 



* American Journal of Science, Vol. VI. (Second Series), July, 1848. 



t De la Beche {Survey of Cornwall), quoting from the MSS. of Mr. Walker, 

 who has devoted much time to the phenomena of tides, says: — " He has found that 

 changes in the height of the water's surface, resulting from changes in the pres- 

 sure of the atmosphere, are often noticed in a good tide-gage before the barom- 

 eter gives notice of any change If tide-gages at important dock-yards 



show that a sudden change of sea-level has taken place, indicative of suddenly 

 decreased atmospheric weight, before the barometer has given notice of such 

 change, all that time which elapses between the notices given by the tide-gage 

 and barometer is so much gained, and those engaged with shipping know the 

 value of even a few minutes before the burst of an approaching hurricane." 



