Improvements in the Surveyor's Compass. 337 



alike produced by sun light, and by galvanic influence. Therefore, 

 it would not appear unreasonable to doubt whether some analogy does 

 not exist between the sun and that force which so strongly affects the 

 magnetic needle. 



I need scarcely mention how extended is the range of galvanic 

 action in almost every part of chemical investigation. There is hard- 

 ly one phenomenon known in chemistry which is not more or less 

 connected with electro-magnetism. In every chemical action, the 

 agency of that force is perceptible, which appears to pervade all na- 

 ture, and whose influence seems to vivify the mutual action of ex- 

 isting bodies. Thus it would appear that the phenomena of gal- 

 vanism, far from being disjoined and unconnected with other classes 

 of corpuscular action, may form the links of that chain by which 

 the mutual action of bodies is joined together. 



Art. XII. — Notice of improvements in the Surveyor's Compass, 

 constructed by Thomas Kendall, of New Lebanon, N. Y. 



The object of the artist in the construction of this instrument has 

 been to simplify and unite in one instrument, of moderate price, all 

 that is necessary or convenient in common practice. The improve- 

 ment, in the form of the needle, has been before the public more 

 than twenty years, and is approved by all who have become acquaint- 

 ed with it. By giving it the form represented in the figure, the ad- 

 vantages of having the points of the needle in a line with the point 

 of the pivot on which it rests, and of having the centre of gravity 

 very low, are secured ; the needle settles with more uniformity, and 

 the vibrations of the lower part of the needle continue, and are plainly 

 seen some time after the points are apparently at rest, giving the as- 

 surance that the needle is free and has settled correctly. Contran 

 to the theories and practice of many, Mr. Kendall has uniformly 

 made his needles with their weight as far removed from the centei 

 as circumstances would admit, on the principle that attraction is ac- 

 cording to the quantity of matter and acts on the needle as a lever, 

 and experience has confirmed the correctness of this opinion. Nee- 

 dles on this plan have been frequently called for by those who were 

 dissatisfied with their old needles, the weight of which was greater 

 near the centre. For ascertaining correctly the variations in degrees 

 and minutes, two limbs are united, one within the other : die outer 

 limb is stationary, being secured fast to the bar of the compass, with 



