Imagine all the soft places of the world, the green valleys, the soft beaches, the tranquil islands, the cool mountains. Now imagine you are on horseback in one of the harshest deserts in the world - riding alone for two years!  That is what famed British naturalist J. Smeaton Chase did. He mounted up and rode into the Mojave Desert to undertake the longest equestrian study of its kind in modern history. Chase was no newcomer to equestrian travel.  In 1910 he rode from the Mexican border to Oregon, then penned a delightful book called ''California Coast Trails,'' which recorded his impressions of the pristine beauty observed during that ocean-front ride. Then in 1916 the amateur naturalist headed his horse inland in search of the secrets of a sun-drenched landscape few had explored. The resulting book, "California Desert Trails," is one man''s love affair with the Mojave Desert. For Chase possessed the rare talent of seeing beauty where others perceived only serpents and sand. He found wisdom in unconventional places, with crazy hermits, wise Indians, and fellow wanderers adrift in the desert. Traveling slowly as he did on horseback, Chase was also able to observe the animals and plants that inhabited this dangerous, but delightful, world. The result is a book unlike any other in the history of equestrian travel. Amply illustrated with stunning black and white photographs which Chase took during his long ride, this poetic travel tale concludes with a special appendix, wherein Chase gives "Hints on Desert Traveling" to a new generation of Long Riders and desert travelers.