Should we inquire into the reasons why raisin grapes may in some localities be grown and actually prove profitable without irrigation; we find the same to depend not alone upon the rainfall of the locality, but principally upon such other circumstances as dew, fog, the nature of the subsoil, and the moisture of the air. In Smyrna the rainfall of the wet season is from twenty-four to thirty-six inches annually, and greater than in any other raisin district. In El Cajon the rainfall is only half that much, and the moisture in this case must be sought partly in the subsoil, which is especially retentive of moisture, as well as in the dew, and the warm fogs from the ocean. The subsoil has the greatest possible influence, as in other valleys near by, where the fog and the dew are the same, but, where the subsoil is different, no raisin grapes can be grown without irrigation. Malaga is in this respect very similar to El Cajon and Sweetwater valleys, but it enjoys more rainfall than the latter places, while probably the dew and fog is about the same. Still in Malaga irrigation is used in a few isolated localities where it can be obtained, the nature of that country being such, that no general irrigation system is possible, and this is probably, more than anything else, the reason why the vines are not more generally irrigated there. In Chile, in the valley of the Huasco, the Muscat vines are grown both with and without irrigation, the conditions there appearing to be very similar to those of El Cajon valley in San Diego county. From the above we might draw a general conclusion, that wherever the raisin-vines cannot grow without irrigation, and wherever water can be had in sufficient quantities, irrigation is practiced in order to increase the crops and to make the business more profitable.