IN CENTRAL AFRICA. 3^1 
But M. Walckenaer does not estimate the other two 
denominations of days' journeys, those of the medium 
and of the light caravans. I shall only remark that the 
result of his arguments seems to be, that the real and 
effective progress is considerably more than 15', and about 
equal to 18' or 19' : the average of a day's journey reduced 
to measures taken in a straight line upon the map. But 
will the diversity of elbows and inflexions, resulting from 
that of the obstacles which produce them, allow us to 
work a uniform reduction, and to apply a uniform factor 
to every distance travelled over ? Let us, for instance 
admit that part of the route amounts to sixty miles, and 
that the straight line between these extremities is forty- 
eight miles ; can the same rule be adopted with regard to 
the whole route, which may be three hundred miles or 
five times as much ? would the total direct line amount to 
two hundred and forty miles ? The longer the route, the 
greater should be the variation in the rate of the reduc- 
tion. The following table contains a summary of these 
observations upon the amount of the hours' and days* 
marches of caravans, and the different computations which 
have been made of them. 
VOC. II. 
Y 
