12 ENGINEERING REPORTS. 
tral point, and I think Chivela will be the best. There, you will start your 
survey of the dividing ridge — perhaps Chivela first, Masdhua next, and Tarifa 
last. Having found the best Pass, run your line down to the Pacific, assuming 
La Ventosa as the terminus. 
" If Tarifa be the best Pass, start from that. In both cases you will be 
able to judge of the practicability of connecting with the lagoons, should the 
Boca Barra be selected. 
" It might prove that not much length would be saved on account of the 
rapidity of descent. Keep your grades below forty feet, if possible ; and tun- 
nel, if necessary and practicable. 
" If Boca del Monte appears to be a good starting point, Mr. Avery might 
commence there, and run towards you ; if not, bring him up to you, and let 
him run a line back, more to the eastward. I shall be able to communicate 
with you before you get to work. 
:t Establish your bench marks so as to be referred to without doubt by 
future surveys. • 
" We must leave out of mind entirely the idea of locating the road ; a demon- 
stration of 'practicability and probable cost is the utmost that we can hope to obtain. 
" As the parties are full in juniors, use them (instead of confining them to 
carrying instruments) as much as possible in lateral reconnaissances, directing 
them to penetrate a certain distance each side of your line, and give you the 
topography, &c, of the country. 
" Your journals should be full as to the survey, and the topographical and 
geological features' and vegetable growth of the country. Note what produc- 
tions are valuable articles of commerce ; what timbers are useful for construc- 
tion; what building stone, &c, is available; and endeavor to ascertain if 
mines and precious metals are likely to be found. 
" It is enjoined upon all individuals attached to the survey, to conduct them- 
selves with the utmost decorum in their intercourse with the natives ; to inter- 
fere with them as little as possible, to pay respect to civil and religious author- 
ities and ceremonies, and in particular to refrain from trespassing on private 
property, taking fruits, &c, &c. Chiefs of parties will be held responsible 
for the good conduct of their respective parties, and will discharge any indi- 
vidul whose conduct does not conform to the stipulations contained in the 
articles he has signed. 
" You will pay particular attention to the use of firearms. They are issued 
exclusively for personal defence, or rather more for moral effect than for any 
anticipated necessity for their use. They should, therefore, not be resorted 
to, even should a quarrel occur, without the utmost caution, as more evil might 
arise from their imprudent use than from being without them." 
Before entering upon the details of our surveys, or the 
manner of operating the parties in the field, it seems proper to 
give a general topographical view of the Isthmus. 
