THE ISLE OF BIRDS. 201 



will not wash them about. Some build grottoes 

 and lattices, thus imprisoning themselves. Other 

 shells burrow deeply in the mud, and others 

 again weave cords of silk to which they fasten 

 themselves." 



" Is it really silk ? " asked Harry. 



" Sufficiently like it to be made into articles 

 of ordinary wear. If you ever visit the British 

 Museum, you will see gloves and other articles 

 made from the silk of the pinna. The threads 

 are fine and of great strength, and when mixed 

 with about one third real silk spun on the dis- 

 taff, form a material of a beautiful brownish- 

 yellow color." 



A noise, heard slightly at first, but now in- 

 creasing to a roaring sound, interrupted the doctor, 

 and as they neared the key it was evident that it 

 proceeded from the black cloud, which began to 

 show its true nature to the astonished party. In 

 a few moments the noise was so great that they 

 could hardly hear each other speak. As they drew 

 near, the birds flew at them with wild cries, as if 

 determined to stop them, then turning suddenly 

 to fly back and rejoin their companions. 



