THE NEVADA TRAVERSE - Nevada Association of Land Surveyors

Terra Incognita... continued from page 27
satisfied he had a consistent result. He did not mention observing
Polaris. He added 0° 16’ for the sun’s semi-diameter and applied
solar declination, made undefined corrections to the tables and
developed his latitudes. He carried a compass, but wrote in the
preface to his diary “...I was not able to obtain a good compass...
although with respect to the directions which I note down I took
the greatest care, I am not altogether satisfied with them for lack
of an instrument. And I have even tried to correct them somewhat
in order to make the map which accompanies this diary in
keeping with the latitudes observed.”
Figure 7. Font’s 1776 map of coastal California and the
Southern Sea
Figure 8. Font’s 1777 map of the Bay of San Francisco
40 The Nevada Traverse Vol. 39, No. 2, 2012
He also specified his unit of length: the Mexican League of 5000
yards or “3000 geometric paces, of which 28 make a degree of
latitude on the earth’s surface” which he paced off against a
measured league prior to leaving. 45 His latitudes are generally
accurate. For example, on February 2, 1776 he observes the
latitude of the Presidio at San Diego as 32° 44’ 30”. He writes
that this agrees with his first observation, taken there on
January 12th. They actually stand at +/-32° 45’ 31”. Observing
at the mouth of San Francisco Bay in March of 1776, he recorded
a latitude of 37° 49’, against an actual latitude of +/- 37° 48’ 39”.
In many cases, however, his values for latitude are somewhat
high, as with other Spanish explorers of that era.
In his own words, Font describes an observation for latitude at
Santa Ana Pueblo, in Sonora, Mexico:
“I observed the latitude of this pueblo with the astronomical
quadrant of the expedition, and, according to the tables of Don
Jorge Juan, without correction I found it to be in 30° 46½’, and
with correction in 30° 38½’ (in fact, it is closer to 30 32½’) . For
greater clarity and satisfaction in all the observations I shall
record the meridian altitude of the sun over the horizon as shown
by the quadrant, to which are to be added sixteen minutes, which
constitute the radius of the solar body, and so I say: at the pueblo
of Santa Ana, October 7, 1775, meridian altitude of the lower
limb of the sun, 53° 28’.”
Nowhere in his diary does Font mention the word longitude,
though it’s possible he had recourse to some methods for finding
it. Though rough longitude was attainable by the method of
lunar distances since 1678, reasonably accurate longitude was
only possible in the field after the 1760’s. But the explorers in
New Spain were either unaware of the technique or lacked the
appropriate timekeeping equipment or almanacs. Nevertheless,
his map (Fig. 7) indicates longitudes, and reflects convergence
of the meridians. Like Kino’s, Font’s longitudes increase west
to east. But there is no mention of a prime meridian; they do
not come near Kino’s values in areas where their maps overlap,
which suggests different meridians. He shows the mouth of San
Francisco Bay at +/-252° 55’. Longitude measured eastward
from the island of Tenerife comes closest at 254° 09’. All that
can be said is that, like Kino’s, Font’s features are proportional
with reality in the areas he actually surveyed. Font also noted
that he borrowed a graphometer 46 from the priests at Mission
Carmel, near Monterey. With it he mapped San Francisco Bay,
Point Arena, Point Reyes and the Farallone Islands. He used
a level to ascertain tidal variations in Suisun Bay. Whatever
their inaccuracies, his maps of the coast of California and San
Francisco Bay (Fig. 8) are immediately recognizable.
Font was an educated man with a flair for writing and a good
head for mathematics and astronomy. He was named to the
expedition for those reasons; that he was a talented musician
was a bonus for the expedition. It is to his credit that, despite
some personality issues with Colonel de Anza and being ill
through most the expedition from Sonora to San Francisco and
back, he took the greatest care in preparing his observations,
field notes and maps, and produced a diary that is regarded to
this day as a classic of western Americana and a primary source
for the history of California and the Southwest. 47
End Notes
1 In 1481 the papal bull Æterni regis had granted all land south of the Canary Islands to
Portugal. However, the voyage of Columbus changed the game. In May, 1493 the Spanish-born
Pope Alexander VI decreed in the bull Inter caetera that all lands west and south of a meridional
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