VI 
INTRODUCTION. 
needle. All this could be taken in at' a glance, and thus the young 
mariner instead of groping his way along until the lights of expe- 
rience should come to him by the slow teachings of the dearest of 
all schools, would here find, at once, that he had already the expe- 
rience of a thousand navigators to guide him on his voyage. He 
might, therefore, set out upon his first voyage with as much con- 
fidence in his knowledge as to the winds and currents he might 
expect to meet with, as though he himself had already been that 
way a thousand times before. 
YI. But, to show the tracks of these vessels on a chart, a line 
had to be drawn for each one ; now this, for so many, and all in 
black or blue, and on the same sheet of paper too, would present, 
it was perceived, a mass of lines in inextricable confusion. More- 
over, after these tracks were projected, there would be no room left 
for the name of the month to show when each one was made, 
much less for any written account of the winds and currents daily 
encountered by each vessel of the multitude. After the tracks 
were projected, there would, it was found after trial, be barely 
room left on the chart to write the name of the vessel, much less 
the direction and set of the winds and currents. 
YII. An appeal, it was consequently decided, should be taken to 
the most comprehensive sense of the five, and it was thereupon re- 
solved to address all those tracks, and winds, and currents, with 
their strength, set, and direction — in short, all this experience, 
knowledge, and information — to the eye, by means of colors and 
symbols. 
YIII. The symbols devised with this view were a comet's tail 
for the wind, an arrow for currents, Arabic numerals for the tem- 
perature of the sea, Roman for the variation of the needle, contin- 
uous, broken, and dotted lines for the moijth, and colors for the 
four seasons. 
IX. A continuous line was used to show that the track was 
made during the first month ; a broken, the second ; and a dotted 
line, the last month of each season : black standing for the winter, 
green for spring, red for summer, and blue for autumn. 
X. The comet's tail, and the arrow, and the numerals, were also 
in colors, according to the seasons. The force and direction of the 
wind, were indicated by the shape and position of this tail ; while 
DSI 
