no PEARLS AND PEARLING 



also serve as rests to hold the bars. These are called 

 half rests, and the bar is first placed on them after be- 

 ing raised out of the water. Then it is raised one end 

 at a time, and placed on the high standards. There is 

 another part of the outfit known as the "mule," which 

 consists of a wooden frame with a heavy cloth tacked 

 over it, with small guide ropes tied to it. 



After the dredge is placed in the water and anchored 

 to the front end of the boat, the "mule" is placed in the 

 water on its edge at the back end of the boat, and at- 

 tached to the boat by the guide ropes. The current of 

 water strikes the broad surface of the "mule," which 

 causes it to pull the boat and dredge. As the dredge is 

 gradually pulled down stream the hooks catch the mus- 

 sels. The usefulness of the appliance depends upon, the 

 habits of the mussels. They rest on the bottom, often 

 partly buried in sand or mud, with the posterior end of 

 their shells facing upstream and partly open to admit the 

 water which contains both oxygen and food. As soon 

 as they are touched they close their shells quickly, and 

 any foreign object which happens to be in the shell is 

 tightly grasped and held. As the dredge is dragged over 

 the mussels the prongs of the hooks enter the open shell 

 and the mussel shells close and grip them tightly. After 

 a sufficient number have become attached, the dredge is 

 raised to the boat. 



Now that a general description of the entire outfit has 

 been given, the parts of the crow-foot dredge will be 

 described separately. Fig. 28 shows the "mule." 



The size of the mule needed will depend upon the 



