Moore at the sheep farm; Henry Moore's Sheep Sketchbook, by Henry Moore and Kenneth Clark. New York: Thames & Hudson Inc. $19.95.

"At first," Henry Moore writes in the short essay included here, "I saw them as rather shapeless balls of wool with a head and four legs. Then I began to realize that underneath all the wool was a body which moved in its own way, and that each sheep had an individual character." In 96 sketches he proves just how diverse and charming is the individual sheep, how gifted and sure the Moore pen. All the same this is a book only for those who are willing to linger lovingly over picture after picture after picture of sheep, and enjoy the diversity of the animals -- all tangled wool and thick heaviness, patient, solid, unmovable, dignified, comic. Still, there is an added delight to be found in the exquisite printing of these facsimiles -- so faithful that it is easy to m istake them for original drawings.