180 Scientific Intelligence. 



20- Auogadro's Multiplying Voltimeter. — This instrument, which differs 

 little from the galvanometer of Schweigger, consists of a sewing needle 

 fixed in the base of a small triangle of paper, passing through two holes 

 in the plane of the paper. It is suspended by a fibre of silk, and is placed 

 above the conducting wire. M. Avogadro prefers that arrangement, 

 as it facilitates the observation of the deviation of the needle, when mea- 

 sured on a graduated semicircle. M. A. has applied the voltimeter 

 to determine the order of the metals, relatively to their electricity, by con- 

 tact. Mem. dell. Acad. Reale di Toritw, torn, xxvii. p. 43. 



METEOROLOGY. 



21. Mean Temperature of the Equator. From a comparison of various 

 observations, M. Humboldt made the mean temperature of the equator 

 81° 5, while Dr Brewster, in his formula?, makes the mean temperature of 

 the equator in the old World 82° 8. This curious subject, however, has 

 been ably discussed in a memoir on refraction and temperature, by Mr 

 Atkinson, who, from a careful examination of Humboldt's observations by 

 the method of minimum squares, has obtained the following results : — 



" 1. The whole of Humboldt's observations, both in Nortli and South 

 America, at or near the level of the sea, indicate that the mean temperature 

 of the equator at the same level is 86° 55 of Fahrenheit. 



"2. AH the observations, nine in number, made within 11° of the equa- 

 tor, where the height does not exceed 3500 feet, indicate that its temperature 

 is 84° 53. But if Caripe be excluded, as it probably ought, the remaining 

 8 give 85° 273, for the mean temperature under the equator. 



" 3. If those places only be taken, which are within the same limits, and 

 whose height is less than 2000 feet, they indicate that the mean temper- 

 ature is 84° 93." 



It thus appears, says Mr Atkinson, from data, furnished by himself, that 

 Humboldt has fallen into an error, when he asserted that the mean 

 temperature of the equator cannot be fixed beyond 81° 5'. 



22. Uiminxdion of the Temperature with the Altitude. — Mr Atkinson has 

 shown that the depression of the thermometer due to the height of 1666 

 feet is 6°. 112, deduced from 128 observations. From 29 other places he 

 proves that the depression of temperature for 1468 feet is 5°.682. These 

 results give nearly 200 feet for 1 degree, and it is remarkable, how very 

 closely they approach to proportionality to the altitudes to which thev be- 

 long, thus confirming Mr Ivory's law. Mr Atkinson's formula for the 

 depression of temperature due to any given altitude, h 



is -J 251.5 + '-(7j — 1) > n=h, where n is the measure of that depression. 



23. Fall of a Meteoric Stone, at Nantgemory, Maryland. — On Februa- 

 ry 10th 1825, between 12 and 1 o'clock, an explosion was heard, louder 

 than that of a cannon, then a loud whizzing noise, and in less than 15 

 minutes, a stone fell, and penetrated about 23 inches into the earth. 



