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133 
prince, was employed in forming a new one, and had 
an appointment bellowed upon him in the emperor’s 
houlehold. About the lame time the duke of juiiers 
and Cleves made him his cofmographei'. In 1551, 
Mercator produced his celeilial globe, which was ac¬ 
companied with a Ihort treatife on the ufeof that inftru- 
ment. Soon after this he removed with his family from 
Louvain, and fettled at Duylburg. Here he pubiiihed, at 
different periods, defcriptions and maps ot the World, 
liiurope, Germany, France, the Britilh lflands, Sec. which 
he afterwards collefted together into an atlas, prefixing 
to them a treatife “ On the Creation and Conftrudlion 
of the World.” His method of laying down charts and 
maps, which is ftill in ufe, and goes by his name, is a 
projedlion of the l'urface of the earth hi piano. See the 
article Geography, vol. viii. p. 365. and Plate XIII. 
lit 1568, Mercator pubiiihed his “ Chronologia a Mundi 
Exordio ad An. Cl3. Iq. LXVIII. ex Eclypiibus, et Ob- 
fervationibus Allronomicis, ac Bibliis, &c.” in folio ; 
and in 1589 he pubiiihed a corrected edition of the Geo¬ 
graphical Tables of Ptolemy. While he was in the midft 
of his labours, and projecting new works for the improve¬ 
ment of geographical fcience, he fell a vidlim to a pa¬ 
ralytic attack in 1594, when in the eighty-third year of 
his age. Belides the articles already noticed, Mercator 
•was the author of, 4. Ratio fcribendarum Literarum La- 
tinarum, quas Italicas curforiafque vocant. 5. De Ufu 
Annuli Aftronomici, 1552. 6. Harmonia Evangeliffarum. 
7. Commentaries on Ezekiel, on the Epiltle to the Ro¬ 
mans, and on the Revelation. 
Mercator had a l'on, named Bartholomew, who wrote 
notes on John Sacrobofco’s Treatife De Sphsra Mundi, 
when he mull have been very young, lince he was only 
eighteen years of age at the time of his death in 1563. 
Melchior Adam. Vit. Germ. Phil. 
MERCA'TOR (Nicholas) an eminent mathematician 
and allronomer, whole name in high Dutch was Kauff¬ 
man, was a native of Danilh Holftein, and born about 
the year 1640. Having early difcovered that he poflefied a 
genius for mathematical ltudies, he received a liberal 
education, fuitable to the bent of his mind, by which he 
was enabled to extend his relearches into the mathe¬ 
matical fciences, and to make very conliderable improve¬ 
ments. It appears, however, both from his own writings, 
and from the charadler given of him by other mathema¬ 
ticians, that his talent rather lay in improving the dif- 
coveries made by others, and in adapting them to ufe, 
than in invention. His genius for the mathematical 
fciences was notwithffanding abundantly confpicuous, 
and introduced him to public regard and elleem in his 
own country, as well as facilitated his correfpondence 
with luch as were eminent in thole fciences, in Den¬ 
mark, Italy, and England. Receiving an invitation from 
fome of his correfpondents to viiit this country, he Ibme 
time afterwards accepted of it, and he fpent the remainder 
of his life in England. He had not been long here before 
he was eledled a fellow of the Royal Society; and he 
afforded frequent evidence of his clofe application to 
lludy, as well as of his great abilities in improving fome' 
branch or other of the fciences. But he is charged fome- 
times with having borrowed the inventions of others, 
and adopted them as his own; and it appeared that, on 
fome occafions, he was not over liberal in his fcientilic 
communications. In proof of this it is oblerved, that 
about the year 1668 lord Brounker publiflied his qua¬ 
drature of the hyberbola, See. which is no other than the 
feries difcovered by Newton. Not long afterwards, this 
quadrature of the hyperbola was demonllrated by Mer¬ 
cator; but by means of the divilion firll made ufe of by 
Dr. Wallis, in his Opus Arithmeticum. Mercator, then, 
could not have any pretence to the dilcovery of the qua¬ 
drature of the hyberbola, fince Dr. Wallis had found the 
divilion long before, and alfo the quadrature of every 
part of the quotient; and this Mercator Ihould have 
acknowledged when he put thofe two inventions to- 
VQL. XV, No. 1030. 
M E R 
gether. It had alfo been oblerved, fome time before 
Mercator announced any thing on the fubjedl, that there 
was an analogy between a fcaie of logarithmic tangents 
and Wright’s'protraction of the nautical meridian line, 
which conlilted of the fums of the fecants ; though it 
does not appear by whom, nor by what accident, this , 
analogy was firll difcovered. It appears, however, to have 
been firll publiflied, and introduced into the practice of- 
navigation, by Henry Bond, who makes mention of this 
property in an edition of Norwood’s Epitome of Naviga-;• 
tion, printed about the year 1645; and he again treats 
of it more fully in an edition of Gunter’s works, printed 
in 1653, where he ftiows how, from this property, to re- 
folve all the cafes of Mercator’s failing by the logarith¬ 
mic tangents, independently of the table of meridional 
parts. This analogy had only been found to be nearly 
true by trials, but not demonllrated to be a mathematical 
property. Such demonftration feems to have been firll . ; 
made by Mercator; who, defirous of profiting by this 
and another concealed improvement of his in navigation, 
invited the public, by a paper in the Philofophicai 
Tranfadtions for June 4, i 665 , to enter into a wager with 
him on his ability to prove the truth or falfehood of the 
fuppofed analogy. This challenge, it feems, was not 
accepted by any one ; and Mercator concealed his de- 
monllration. It excited, however, the attention of ma¬ 
thematicians to the fubjedl, and demonllrations were not 
long wanting. But, notwithffanding the inftances above 
related of Mercator’s difingenuoulhefs and want of be¬ 
coming liberality, he dillinguilhed himfelf by the publi¬ 
cation of many valuable pieces on philofophicai fubjedls ; 
the principal of which are enumerated below. He died 
in 1594, about the age of fifty-four. He at one time 
made a fruitlefs attempt to reduce aftrology to rational 
principles. His principal produdlions are, 1. Cofino- 
graphia, five Delcriptio Cadi et Terrs in Circulos, qua 
Fundamentum llernitur Sequentibus Ordine Trigono- 
metris Sphericorum Logarithmics, Affronomics, See. 
Dantzic, 1651, nmo. 2. Rationes Mathematics Sub¬ 
duals Anno 1653 ; Copenhagen, 4to. 3. De Emenda- 
tione Annua Diatribs dus, quibus exponuntur et de- 
monftrantur Cycli Solis et Luns, &c. 4to. 4. Hypothefis 
Allronomica nova, et Confenfus ejus cum Obfervationi- 
bus ; Lond. 1664, folio. 5. Logarithmo-technia, five Me- 
thodus conffruendi Logarithmos, nova, accurata, et fa- 
cilis, &c. accedit vera Quadratura Hyperbols, et In- 
ventio Summs Logarithmorum, &c. Lond. 1668, 4to. 
6. Inllitutionum Affronomicarum Libri duo, de Motu 
Aftrorum communi et proprio, fecundum Hypothefes 
veterum et recentiorum prscipuas, &c. 1676, 8vo. and 
he communicated to the Royal Society leveral papers, 
which are inferted in the firll, third, and fifth, volumes 
of the Philofophicai Tranfadtions. Gen. Biog. 
MERCATO'RUM FES'TUM, was a feftival kept by 
the Roman merchants on the 15th of May, in honour of 
Mercury, who prelided over merchandile. A low was fa- 
crificed on the occafion, and the people prefent fprinkled 
themfelves with water fetched from the fountain called 
Aqua Mcrcurii; the whole concluding with prayers to the 
god for the prolperity of trade. 
MER'CATURE, f. [ mercatura , Lat.] The practice of 
buying and felling. 
MERCA'TUS, or Merca'do (Louis), an eminent phy- 
fician of the fixteenth century, was born at Valladolid in 
Spain, where he became a medical teacher, and obtained 
luch reputation as led to wealth and honourable appoint¬ 
ments. He was firll phyfician to Philip II. during a pe¬ 
riod of twenty years ; and, on the death of that prince 
in 1598, was nominated to the fame office by his fon and 
fuccelfor Philip III. Mercado lived to the age of eighty- 
fix ; but the latter years of his life were rendered painful 
by the Hone. He was author of a conliderable number 
of works relative to medicine and furgery, written in a 
better Latin ftyle than moll of thofe compofed by the 
writers of Spain 5 neverthelefs, they are chiefly borrowed 
M m from 
