Edmond inserted his lever in the ring and exerted all his strength ; the flag-stone yielded , and disclosed steps that descended until they were lost in the obscurity of a subterraneous grotto .
In summary , as for the six chemical indexes , recycled water irrigation can increase the content of the relevant elements in subterraneous water and soil , but whether the effect is safe requires further study ; as for plant growth , certain chemical elements in recycled water is conducive to plant growth .
