346 Dr. John Davy on the aqueous solution of 



is of the order m\ or at least such portion of it as is supposed 



tobeincludedinthis expression; and as -, — ,— and-. — are each 

 r dedc a c 



of the order m\ this term is of the order m 6 , which after a 

 fresh integration remains of the order ?n 4 . 



Hence we may conclude with safety, without having re- 

 course to any peculiar system of constants, or to any preca- 

 rious induction, that however far the approximation be car- 

 ried, the variation of the semi-axis major in the Lunar Theory 

 contains no term of long period multiplied by a power of m 

 inferior to the fourth. 

 Sept. 21, 1840. 



LI. Some Observations on the aqueous Solution of Carbonate 

 of Magnesia with excess of Carbonic Acid, and on the Salt 

 which it affords by spontaneous Decomposition, By John 

 Davy, M.D., F.R.S* 



I HAVE been induced to institute some experiments on the 

 solution of carbonate of magnesia in water strongly im- 

 pregnated with carbonic acid gas, in consequence of the high 

 repute, on very questionable grounds, which it has lately ac- 

 quired as a medicine. 



The solution I have used is that prepared and sold by Mr. 

 Dinneford of New Bond-street, with the designation of Dinne- 

 ford's Solution of Magnesia, and with the following recom- 

 mendation on the label: " The great advantages of this elegant 

 preparation are, that being in a fluid state and possessing all 

 the properties of magnesia in general use, it is not likely to 

 form dangerous concretions in the bowels ; it corrects acidity 

 and heart-burn effectually, without injuring the coats of the 

 stomach, as carbonates of potash and soda are known to do ; 

 it prevents the food of infants turning sour, and in all cases 

 it acts as a pleasing aperient, particularly adapted for fe- 

 males." 



Such a recommendation I should not have thought it right 

 to notice, were it an ordinary quack eulogy, and unsupported 

 by certificates given by respectable medical men ; and more- 

 over were I not assured that great faith is placed by many 

 persons in the asserted virtues of the preparation, and that 

 the use of it is rapidly extending. 



The first trials I subjected the medicine to, were made 

 with a view to test the permanence of the solution ; as by ex- 



* Communicated by Sir David Brewster. 



