So far, Bissell's enterprise seemed to promise success, yet the great problem still remained: how could he obtain this rock oil in amounts large enough to make his enterprise a practical one?

至此，Bissell 的事业似乎有望成功， 但仍然存在一个大问题：他如何才能获得足够数量的这种岩石油， 使他的事业切实可行？