By comparison and analysis of the optical data of the two galactic clusters of Pleiades and h and x Persei and the radio data of the HI gas clouds which are related with those two clusters, the relative motions of those gas clouds with retpect to the two clusters were obtained. The three theories on the acceleration of HI gas cloud surrounding a star cluster by Blaauw. Oort and Spitzer, and Kahn were examined with the above obtained kinetic data of the Pleiades and the h and x Penei clouds. And it was shown that Blaauw's theory is applicable to the h and x Persoi clouds but not to the Pleiades, that Dart and Spitzer's theory can explain the motions of both clouds, and that Kahn's theory needs more improvement to be a complete one.

Abstract
Ⅰ. 緖論
Ⅱ. 觀測 Data의 分析과 gas clouds의 運動
Ⅲ. 理論의 適用과 計算
Ⅲ. 結論과 展望
附記
參考文獻

• 兪景老(Earth Science Department, College of Education, Seoul National University) | Kyung Loh Yu