382 Intelligence and Miscellaneous Articles. 



according to powers of M and M', and then by two multiplications 



to find —r . 



" The terms of the second order admit of being easily obtained 

 according to this method by means of Taylor's theorem, since the 

 quantities x, y, z are only involved, the perturbations of which are 

 already known. But this process of calculation, which in every 

 case is very troublesome, would be useless when the question refers 

 to the small planets, since the elements of these bodies are not known 

 with sufficient accuracy. Dr. Briinnow, by means of his osculating 

 elements, has obtained pretty accurate values of the disturbing 

 forces ; and by applying the resulting perturbations has deduced the 

 mean elements of the planet. To me it is as good as certain that 

 the perturbations thus calculated (the hundredths of seconds are 

 omitted) are sufficiently accurate to be employed next year for a 

 more exact determination of the mean elements. The terms of the 

 first power of the masses which are here given will therefore subserve 

 the object in view, and on a future occasion the question may be 

 investigated, whether the terms of the second order exercise any 

 sensible influence. 



" The perturbational values are all given as they follow from the 

 calculations. Moreover, the secular equations of the elements which 

 might be deduced from the terms involving t (the unit of t is the 

 Julian year) are not deduced, since for the next year the calculation 

 in its present form is more convenient. By the way, I see that I 

 have not made any mention of these terms in speaking of the inte- 

 gration of the differential equations. However, what I have said 

 above will be quite sufficient to give you an idea of this method of 

 computing the perturbations." 



" Berlin, April 24, 1863." 



LX. Intelligence and Miscellaneous Articles. 



ON THERMIC CONDUCTION IN METALS. BY G. GORE, ESQ. 



n[ ^HE following experiments were made to ascertain if, in the case 

 •*■ of thermic conduction between different metals, or between 

 similar metals but of different sizes, the rapidity of conduction was 

 affected by the direction of transmission ; for instance, to ascertain 

 if thermic conduction was more or less rapid when heat passed from 

 an iron wire to a copper one, than when it passed from the copper 

 to the iron ; or from a small iron wire to a larger one than vice versd. 

 The arrangement adopted was, to form compound bars of the 

 metals to be tested by taking equal lengths of each and soldering 

 them end to end ; then taking two such compound bars, each of 

 similar metals, and after sloping one end of the dissimilar metals in 

 each, soldering them together at those parts so as to form a double 

 compound bar or triangle of an acute V form, each limb of which 



