570 L A W. 
the common law, is yet ingrafted into it, and made a part 
of it; being allowed, for the benefit of trade, to be of the 
utmoft validity in all commercial tranfailions; for it is a 
maxim of law, that cuilibet in fua arte credendum eji. 
The Lex mercatoria, or the cuftom of merchants, like 
the lex et confuetudo parliament, however, defcribes only a 
great divifion of the law of England, The laws relating 
to bills of exchange, infurance, and all mercantile con¬ 
tracts, are as much the general law of the land as the 
laws relating to marriage or murder ; but the merchants 
have been frequently led to fuppofe, that all their new 
fafhions and devices immediately became the law of the 
land : they ought however to take their law from the 
courts, and not the courts from the merchants; and, 
when the law is found inconvenient for the purpofes of 
extended commerce, application ought to be made to 
parliament for red refs; for, as Mr. J.uftice Fofter has ob- 
ferved, (2 Burr, 12.26.) the cuitom of merchants is the 
general law of the kingdom, and therefore ought not to 
be left to a jury after it has been fettled by judicial de¬ 
terminations. 
The rules relating to particular cuftoms regard either 
the proof of their exiltence; their legality when proved ; 
or their ufual method of allowance. And firft: we will con- 
lider the rules of proof. 
As to gavelkind and borough Englilh, the law takes 
particular notice of them ; and there is no occafion to 
prove that fuch culioms actually exift, but only that the 
lands in queftion are fubjeft thereto. All other private 
cuftoms muft be particularly pleaded; and as well as the 
exiftenceof fuch cuftoms muft be Ihown, as that the thing 
in diftpute is within the cuftoms alleged. The trial in 
both cafes (both to (how the exiftence of the cuftom, as, 
S£ That in the manor of Dale lands (hall defcend only to 
the heirs male, and never to the heirs female;” and alfo 
to (how “ that the lands in queftion are within that ma¬ 
nor”) is by a jury of twelve men, and not by the judges; 
except the fame particular cuftom has been before tried, 
determined, and recorded, in the fame court. 
The cuftoms of London differ from all others in point 
of trial; for, if the exiftence of the cuftom be brought in 
queftion, it fhall not be tried by a jury, but by a certifi¬ 
cate from the lord mayor and aldermen by the mouth of 
their recorder; unlefs it be fuch a cuftom as the corpora¬ 
tion is itfelf interefted in, as a right of taking toll, Sec. 
for then the law permits them not to certify on their own 
behalf. And, when a cuftom has been once certified by 
the recorder, the judges will take notice of it, and not 
fuft'er it to be certified a fecond time. 
When a cuftom is actually proved to exift, the next in¬ 
quiry is into the legality of it; for, if it is not a good cuf¬ 
tom, it ought to be no longer ufed. Malm ufus abclendus 
ef, is an eftablifhed maxim of the law. To make a par¬ 
ticular cuftom good, the following are necelfary requi- 
fites: 
1. That it have been ufed fo long, that the memory of 
man runneth not to the contrary. So that if any one can 
fhow the beginning of it within legal memory, that is, 
within any time fince the firft year of the reign of Ri¬ 
chard I. it is no good cuftom. For which reafon no cuf¬ 
tom can prevail againft an aft of parliament; as, if it be 
pleaded as a cuftom that every pound of butter (hall weigh 
18 ounces inftead of 16, it is bad, becaufe the 13 and 14. 
Car. II. c. 26, direfts that every pound throughout the 
kingdom fhall weigh 16 ounces only. 
2. It muft have been continued. Any interruption would 
caufe a temporary ceafing; the revival gives it a new be¬ 
ginning, which will be within time of memory, and there¬ 
upon the cuftom will be void. But this muft be under- 
ftood with regard to an interruption of the right; for an 
interruption of the pofleffion only for ten or twenty years 
■will not deftroy the cuftom. As if the inhabitants of a 
parifti have a cuftomary right of watering their cattle at 
certain pool, the cuftom is not deftroyed, chough they do 
not ufe it for ten years; it only becomes more difficult 
to prove; but, if the right be any how dfcontinued for a 
day, the cuftom is quite at an end. 
3. It muft have been peaceable, and acquiefced in; not 
fubjeft to contention and difpute. For, as cuftoms owe 
their original to common content, their being immemori- 
ally difputed, either at law' or otherwife, is a proof that 
fuch content was wanting. 
4~ Cuftoms muft be reafonable ; or rather, taken nega¬ 
tively, they muft not be unreafonable. Which is not al¬ 
ways, as fir Edward Coke fays, to be underftood of every 
unlearned man’s reafon; but of artificial and legal reafon, 
warranted by authority of law. Upon which account a 
cuftom may be good, though the particular reafon of it 
cannot be aftigned ; for it iufficeth, if no good legal rea¬ 
fon can be aftigned againft it. Thus a cuftom in a parifti, 
that no man fhall put his hearts into the common till the 
third of Oftober, would be good ; and yet it would be 
hard to fhow the reafon why that day in particular is fixed 
upon rather than the day before or after. But a cuftom, 
that no cattle fhall be put in till the lord of the manor 
has firft put in his, is unreafonable, and therefore bad; 
for peradventure the lord will never put in his; and then 
the tenants will lofe all their profits. 
5. Cuftoms ought to be certain. A cuftom, that lands 
fhall defcend to the molt worthy of the owner’s blood, is 
void; for how fhall this worth be determined ? but a cuf¬ 
tom to defcend to the next male of the blood, exclufive 
of females, is certain, and therefore good. A cuftom to 
pay twopence an acre in lieu of tithes, is good ; but to 
pay fometimes twopence and fometimes threepence, as the 
occupier of the land pleafes, is bad for its uncertainty. 
Yet a cuftom, to pay a year’s improved value for a fine 
on a copyhold eftate, is good ; though the value is a thing 
uncertain ; for the value may at any time be afcertained ; 
and the maxim of law is, Id certum ef, quod cerium reddi 
potejl. But a cuftom that poor houfekeepers fhall carry 
away rotten wood in a chafe is bad, being too vague and 
uncertain. 2 T. R. 758. To which we may add, that a 
cuftom that poor people fhall carry away every thing they- 
can lay their hands on is bad; yet the memory of man run¬ 
neth not to the contrary. 
6 . Cuftoms, though eftablifhed by confent, muft be 
(when eftablifhed) compulfory ; and not left to the option 
of every man, whether he will ufe them or no. There¬ 
fore a cuftom that all the inhabitants fhall be rated toward ’ 
the maintenance of a bridge, will be good ; but a cuftom, 
that every man is to contribute thereto at his own plea- 
fure, is idle and ablurd, and indeed no cuftom at all. 
7. Laftly, Cuftoms muft be conffent with each other. 
One cuftom cannot be fet up in oppofition to another. 
For, if both are really cuftoms, then both are of equal an¬ 
tiquity, and both eftablifhed by mutual confent; which, 
to fay of contradiftory cuftoms, is abfurd. Therefore, if 
one man prefcribes that by cuftom he has a right to have 
windows looking into another’s garden, the other cannot 
claim a right by cuftom to flop up or obllruft thofe win¬ 
dows ; for thefe two contrndiffory cuftoms cannot both 
be good, nor both ftand together. He ought rather to 
deny the exiftence of the former cuftom. 
Next, as to the allowance of fpecial cuftoms. Cuftoms, 
in derogation of the common law, muft be conftrued 
ftriftly : and this rule is founded upon the confideration, 
that a variety of cuftoms in different places upon the fame 
fubjeft is a general inconvenience ; the courts therefore 
will not admit fuch cuftoms but upon the cleareft proof. 
Thus, by the cuftom of gavelkind, an infant of fifteen 
years may by one fpecies of conveyance (called a deed of 
feoffment ) convey away his lands in fee fimple, or for ever. 
Yet this cuftom does not empower him to ufe any other 
conveyance, or even to leafe them for feven years ; for 
the cuftom muft be ftriftly purfued. So, where there is 
a cuftom that lands fhall defcend to the eldeft filter, the 
courts will not extend this cuftom to the eldeft niece, or 
to any other eldeft female relation, but upon the fame au¬ 
thority by which the cuftom between filters is fuDporred. 
‘ 1 T.R, 
