Prof. Challis on the Theory of the Moon's Motion. 201 



Temperature. Volume. 

 °C. 



at 000862 



5 0-00760 



10 ........ 0-00681 



15 000626 



20 0-00595 



Hence it follows that the amount of carbonic acid which a cubic 

 millimetre of the sap* from the leaves exposed to the air is able 

 to absorb at 15° and m, 76 pressure, is never more than 0-000415 

 cubic millimetre, whilst the moisture in the loose earth around 

 the roots may contain 0-00626 cubic millimetre, or nearly fifteen 

 times as much. The great productiveness of mould rich in 

 humus, and a part of the advantages which the agriculturist 

 derives from breaking up his land, is easily explained from these 

 phsenomena. 



The phfenomena of the oceanic atmosphere, as well as of the 

 absorption of air in the blood, which are deducible from the law 

 of absorption, I reserve for my own future investigation. 



It must also remain for future research to estimate again with 

 all the exactitude necessary for normal determinations, the absorp- 

 tion-coefficients detailed in the present memoir, an absorptiometer 

 of larger dimensions being made use of. When these experi- 

 ments are carried out, it will be possible to determine the limits 

 at which the law of absorption, similarly to that of Mariotte, 

 begins to be disturbed by foreign influences. 



In conclusion, my best thanks are due to Mr. Roscoe, who has 

 kindly translated this memoir into English. 



Heidelberg, February, 1855. 



XXVIII. The Theory of the Moon's Motion. — Explanation of the 

 occurrence of non-periodic Factors in the Development of the 

 Radius-vector. By Professor Challis f. 



IN the Postscript to my communication to the Philosophical 

 Magazine for February (p. 137), I have stated that the oc- 

 currence of terms containing factors which may increase indefi- 

 nitely with the time in the development of the moon's radius- 

 vector, is not owing to the circumstance that the approximation 

 commences from a fixed ellipse, as has been generally admitted, 

 but is wholly due to the mode of integration. I now propose to 

 explain why one mode of integration rather than another leads 



• Here the average amount of carbonic acid in the air is taken, and the 

 absorption-coefficienti of the sap considered the same as those of water. 

 t Communicated by the Author. 



