348 Miscellanies. 



and are pursued with advantage ; both are necessary to render the ac- 

 count of a chemical compound complete, and the teacher or writer 

 will, therefore, act his own judgment, as to the precedence which may- 

 be given to the one or to the other, when both modes are practicable. 

 For example, the compound fluid, water, may be first described, as 

 having certain physical and chemical properties : it may then be de- 

 composed, say by the galvanic power, and its elementary gases obtain- 

 ed, distinct, or in mixture; those elements, after having been sepa- 

 rately exhibited and described, may then be combined, by slow com- 

 bustion, or by explosion, and the water reproduced ; — thus, synthesis 

 will follow analysis, and both modes united, give all the demonstra- 

 tion which the case admits of. The opposite order may, in this case, 

 be pursued with perhaps equal advantage. This is a familiar example. 

 It may be added, that in the history of the combustibles, and of the 

 metals, it is usual to proceed synthetically, exhibiting the simple body 

 first, and then its compounds; but, with respect to the metals which are 

 the bases of the alkalies and earths, the opposite course appears to 

 be the most eligible ; the alkalies and earths being described first, 

 we then proceed, analytically, to their decomposition, and return, 

 synthetically, to their recomposition ; and thus we arrive at the same 

 result, which, in a different order, is usually pursued with respect to 

 the other bodies.* 



But, granting that the alkalies and earths are to be placed between 

 oxygen and the metals, should they precede or follow the simple 

 combu^ibles ? In my courses of instruction, I formerly placed the 

 combustibles first, and this order has much to recommend it ; after- 

 wards, following some of the earlier editions of Dr. Henry's Chem- 

 istry, (which was then, and for many years after, my text book,) I 

 placed the alkalies and earths before the combustibles, and I am, on 

 the whole, disposed to regard this order, as presenting fewer practical 

 difficulties, in teaching, than the other ; but it is not very important 

 which is preferred. In Dr. Murray's Elements — (now in its sixth 

 edition,) after oxygen, the atmosphere and water, are placed the 

 combustibles; to them succeed chlorine, iodine and bromine; then 

 follow the alkalies, and the earths and their bases, and thus we pass, 

 by an agreeable and natural transition, to the entire class of metals. 

 This arrangement is both logical and convenient ; perhaps it is the 

 best that can be devised. 



* In order to understand the metallic character of the bases of the alkalies and 

 earths, no more knowledge of metals is necessary, than every one possesses. 



