I advanced this theory to account for the origin of whirlwinds in a paper read before the Philosophical Institute of Victoria in 1857. It was afterwards communicated by the Astronomer-Royal to the "London Philosophical Magazine", where it appeared in January 1859. A suggestion that I at the same time offered, that the opposite rotation of cyclones in the two hemispheres was due to the same causes as the westerly deflection of the trade-winds from a direct meridional course, has been generally adopted by physicists, and I am not without hopes that the main theory may also yet be accepted; but whether or not, I am confident that a study of the smaller eddies of air is the proper way to approach the difficult question of the origin of cyclones.

CHAPTER 17.

Cattle-raising. Don Filiberto Trano's new house. Horse-flies and wasps. Teustepe. Spider imitating ants. Mimetic species. Animals with special means of defence are conspicuously marked, or in other ways attract attention. Accident to horse. The "Mygale." Illness. Conclusion of journey.

AFTER crossing the trachytic plain, we reached a large cattle hacienda, and beyond, the river Chocoyo, on the banks of which was some good, though stony, pasture land. We saw here some fine cattle, and learnt that a little more care was taken in breeding them than is usual in Nicaragua. The country, with its rolling savannahs, covered with grass, is admirably suited for cattle-raising, and great numbers are exported to the neighbouring country of Costa Rica. Scarcely any attention is, however, paid to the improvement of the breeds. Few stations have reserve potreros of grass. In consequence, whenever an unusually dry season occurs, the cattle die by hundreds, and their bones may be seen lying all over the plains. Both Para and Guinea grass grow, when planted and protected, with the greatest luxuriance; and the latter especially forms an excellent reserve, as it grows in dense tufts that cannot be destroyed by the cattle. When not protected by fencing, however, the cattle and mules prefer these grasses so much to the native ones, that they are always close-cropped, and when the natural pasturage fails there is no reserve of the other to fall back on. I planted both the Para and Guinea grasses largely at the mines and at Pital, and we were able to keep our mules always in good condition with them.