(5 
ROTATION. 
The numbers thus prefixed are called coefficients ; 
and that quantity which stands without a coefficient is 
always understood to have an unit prefixed, or to be 
taken once, and no more. 
Those quantities are said to be like that are expressed 
by the same letters under the same powers, or which 
differ only in their coefficients: thus 3be, bbr, and 8be 
are like quantities ; and the same is to be understood of 
the Radicals 2 y aml 7 \/ But unlike 
quantities are those which are expressed by different 
letters, or by the same letters under different powers : 
thus <2ab, <2abc, bcitf, and 3ba z , are all unlike. 
When a quantity is expressed by a single letter, or by 
several single' letters joined together in multiplication 
(without any Sign between them) as a, or 2ab, it is 
called a simple quantity. 
But that quantity which consists of two or more such 
simple quantities, connected by the signs + or —, is 
called a compound quantity; thus a — 2ab 4- babe is a 
compound quantity ; whereof the simple quantities a, 
2ab and babe are called the Tertis or Members. 
The letters by. which any simple quantity is expressed 
may be ranged according to any order at pleasure, and 
yet the signification continue the same : thus ab may 
be wrote ba ; for ab denotes the product of a by b, and 
ba the product of b by a ; but it is well known, that, 
when two numbers are to be multiplied together, it 
matters not which of them is made the multiplicand, 
nor which the multiplier, the product, either way, 
coming out. the same. ,In like manner it will appear 
that abe, acb, bac, bca, cab, and eba, all express the same 
thing, and may be used indifferently for each other (as 
will be demonstrated further on) ; but it will be some 
times found convenient, in long operations, to place the 
several Lett ers according to the order which they obtain 
jn the alphabet. 
Likewise the several members, or terms of which 
any quantity is composed, may be disposed according 
to any order at pleasure, and vet the Signification be no 
ways affected thereby. Thus a — 2ab t- ba'h may 
be wrote a f 5a z b — 2ah, or — 2ab f a f 5a z b, &c. 
for all these represent the same thing, viz. the quantity