312 Scientific Intelligence. [Oct. 



cracking. The gentleman who communicates the method says, 

 that he has often cooled such glass to the temperature of 10°, 

 and poured boiling water into them without experiencing any 

 inconvenience from the suddenness of the change. 



If the glasses are to be exposed to a higher temperature than 

 that of boiling water, he proposes boiling them in oil. 



IV. On the different Quantities of Rain collected in Rain-Gauges 

 at different Heights. By Mr. Meickle. 



(To Dr. Thomson.) 

 SIR, 35, Berner's-street, Aus. 25, 1813. 



In the Annals of Philosophy for August, I perceive a very 

 superficial attempt to account for the difference observed in the 

 results of rain-gauges placed at the top and bottom of a building. 

 The author, M. Flaugergues, with the utmost certainty, ascribes 

 it to the wind's altering the general direction of the rain ; and 

 seems, with all due solemnity, to demonstrate, by means of a 

 diagram too, that " the quantity of rain which enters the rain- 

 gauge is proportional to the sine of the inclination of the rain." 



This explanation is no doubt very satisfactory to that class of 

 readers who rest all on authorities, and never think for them- 

 selves. But the slightest reflection is sufficient to lay it aside 

 altogether. It is easy to see, that the horizontal distance of the 

 lines in which the rain falls is absolutely independent of their 

 inclination, being accurately the same where the wind runs 

 steadily 60 miles an hour, as if it were a perfect 

 calm. By merely looking at the figure, it is plain 

 that a gauge of the width, A B, will there receive 

 the drops falling obliquely, just the same as after 

 they become perpendicular in the calm at C D.* 



Such an explanation, therefore, as that of M. Flau- 

 gergues, has no concern with the case under consi- 

 deration. Nothing indeed can be more vague than some 

 conclusions which he draws from his doctrine, respecting the 

 proper position of a rain-gauge. Were his opinion really correct, 

 the quantity of rain which falls in any place would depend 

 chiefly on the state of the wind. The very injudicious way in 

 which he has drawn his diagram is sufficient to lead thousands 

 into the same mistake. 



I can hardly pretend to give a complete solution of this well- 

 known paradox ; but am disposed to think it is some way owing 

 to the obstruction which the gauge itself offers to the wind. 

 Perhaps the wind's being made to rush with greater rapidity, 

 and a little upward in beginning to pass over the mouth of the 

 gauge, prevents the rain from falling into that part of it which is 

 jiext the wind. A sudden or abrupt increase of the wind's 



* Tn strictness, the drojis fall in curves, but this is sufficient to show the truth of 

 ihe above observation. 



