and gardens where, instead of the thorn, should come up the fir-tree, and instead of the briar the myrtle-tree. The most obvious of these is to construct strong barriers at the foot of some of the lower ravines of the Elburz mountains, the chain of which lies ten miles to the north of Tehran. The whole chain is covered with snow each year from top to bottom, and from October till April the whole of the upper part for a height of thousands of feet remains white. In April and May this precious snow melts and flows down through the ravines, and inundates the plain, which at that season is in no want of an extra supply of water. But were a series of reservoirs constructed, as they very easily might be, at the foot of the rocky ravines, the precious fluid would be saved and would be available for use in the succeeding months.
Means might be had recourse to for supplying the district of Tehran with water even on a larger scale than would be yielded by the adoption of the plan indicated above. The country to the north of the Elburz mountains happens to be as abundantly supplied with streams of water as the plain to the south of that chain is destitute of them. If the course of one of these rivers could be diverted towards the south a great boon would be conferred on one district and no loss inflicted on the other, and it is the opinion of engineers that, by cutting out a new channel for one of these streams from a point sufficiently high, a river might be turned, by the aid of some tunnelling, into the plain of Tehran. Every drop of water that is brought supplies the means of extending the cultivation, and thus of attracting a greater fall of rain. It is observed that the yearly fall of rain in the
