22fi On the Comparative action of Aneroid Barometers. [No. 3. 



the Inertia. Perhaps if the Aneroid had been gently tapped with a 

 fillip of the finger it might have shewn a greater fall. If it did not 

 do so, then the difference of pressure was so gradual that it could not 

 overcome the Inertia and friction. It is true that the motion of the 

 vessel must have disturbed or done away with the Inertia of the 

 Barometric column, but that of the leathern bag, or its inflexibility 

 rather, still remains. 



And thus we arrive at what I set out with, viz. that in a great 

 change of atmospheric pressure, without much if any change of tem- 

 perature, the Simpiesometer would be found the most sensitive instru- 

 ment as regards time. In this case though not an extreme one it has 

 been so found, and I have endeavoured to assign a reason for it. We 

 must wait to see if other instances will confirm or modify these views. 



I do not consider this instance the less valid that it was one of those 

 in which the Barometer failed to give very timely warning, (though 

 enough for every vigilant seaman when the other premonitory signs of 

 the weather were taken into account), and was moreover one in which 

 the total depression of the instruments was very small. It is exactly 

 in cases like this that the seaman, and especially if in a short-handed 

 merchantman, requires the aid of the most sensitive of the forewarning 

 instruments, the instrument warning him to watch the weather, and 

 the weather sending him to look at his instrument. For the present 

 the Aneroid has not at all justified Mr. Dent's anticipation (p. 32 of 

 his treatise on the Aneroid) of its " responding in a moment to the 

 influence of atmospheric pressure. " The Sailors will think also with 

 me that it will be some little time before we shall have a chance of 

 seeing Mr. Dent's exemplification of the convenience of the Aneroid 

 verified, which I copy here as an amusing instance of the facility with 

 which men may be led by their desire to recommend a new and 

 favourite instrument to advance confidently what is in effect a sheer 

 nonsensical puff. 



"As an exemplification, it may not be amiss to lay before the nautical man the 

 case of his being, while in his cabin, made sensible, by means of the Aneroid, of 

 a sudden change likely to take place in the atmosphere. An important alteration 

 might be immediately necessary in the adjustment of sails, &c, which, by the 

 timely information afforded him through the Aneroid, he would at once have 

 accomplished, long before the common Marine Barometer had even signified the 



