314 AGRICULTURAL REPORT. [1677, G78, 679, 680 



The same is the case at Grand Gulf, where this material is seen in a vertical 

 well of about 50 feet, at the S. end of the ridge which, a few hundred yards 

 above, bears but a few feet of it on top of the rock — the Grand Gulf sandstone 

 (1T232). 



677. In steep, vertical, and even overhanging slopes, the calcareous silt resists 

 the action of water remarkably well. The cause of this phenomenon is probably 

 to be sought in the circumstance, that the loose silicious material, which by 

 itself would be very readily carried off by water, is to some extent cemented by 

 the lime contained in the mass. In fact we find in many cases, that the surface 

 exposed to the atmosphere has hardened into a kind of crust, by the deposition 

 of calcareous matter ; which, of course, adds greatly to the stability of the 

 slopes. When, however, the continuity of the mass is once broken, the loose 

 material is washed away by the rains with great ease and rapidity. 



678. This peculiarity is the cause of a phenomenon which at first strikes the 

 traveller as indicating a very singular system of road engineering among the 

 inhabitants. Whenever the road crosses a hill or spur of a ridge, we observe 

 hillside cuts with vertical walls, which allow the vehicle to advance horizontally 

 into the hill for some distance, when there is a sudden, steep ascent, rising up 

 very nearly to the original summit of the hill ; then we find on the other side 

 of the sharp crest, a descent as steep as the ascent was. Of course, this is 

 anything but an advantage over the original status, when there was a gradual 

 slope all the way up ; for the weight has to be lifted to the same height as was 

 originally the case, while the sudden strain consequent upon the steepness of 

 the slope, as at present existing, adds greatly to the labor of the team. 



According to the accounts of the inhabitants, however, this state of things is 

 brought about chiefly by the rain water during the wet season. The silt being 

 broken up in the road by the wagons, is copiously washed away on the slopes, 

 while on the summit, where the mass of water, as well as its velocity is small, 

 it is to a great extent absorbed, and the worked up mass settles down again into 

 its compact condition, so as to scarcely detract from the height of the hill. 

 When subsequently the roads are worked, the loose material on the slopes is 

 still further removed, and perhaps some more of it loosened to fill up holes ; 

 while the summit is left untouched, as no obvious obstacle exists there. Thus 

 we sometimes find in these cuts, hillocks crossing the road, whose sharp crest 

 almost touches the perch-pole of the wagon, while the front wheel is going down, 

 and the hind wheel running up hill. 



679. It might seem frivolous to treat with such speciality of a subject like 

 this ; but cases like the one just alluded to, where the removal of half a dozen 

 cartloads from the crest of the hillock would lower it by several feet, are of such 

 constant occurrence, as to make the labor which might be saved in so simple a 

 manner, a matter worthy of serious consideration. Not a few persons appear 

 to be under the impression, that after all there is some gain in being able to go 

 horizontally for a greater distance, and having the slope shorter. But it is a 

 principle of mechanics well settled, that the height to which a weight requires to 

 be lifted, is the measure of the force required to accomplish the work. And it is 

 just as well settled, that a steady strain causes much less wear and tear to 

 everything, than a succession of j irks — such as are caused by these sudden 

 rises and falls. 



680. The denudations- of the calcareous silt iu question are not, 

 however, the only cause of the hilliness of this region. Two cases 

 have already been mentioned, in -which the greater part of the 

 ridges is formed by tertiary rocks (Vicksburg and Grand Gulf) ; 

 and rocks or clays of the same age are very generally found form- 

 ing the lower portion of the ridges bordering the larger water- 



*" Washing away." 



