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377.  Different  Screws  on  the  same  Axis 414

378.  Co-ordinates  of  the  Restraining  Wrench  for  a  Free  Rigid  Body       .         .  414

379.  Limitation  to  the  position  of  the  Restraining  Screw          ....  416

380.  A  Verification 416

381.  A  Particular  Case 417

382.  Remark  on  the  General  Case 418

383.  Two  Degrees  of  Freedom 419

384.  Calculation  of  T 420

385.  Another  Method 420

386.  The  Permanent  Screw 421

387.  Geometrical  Investigation 422

388.  Another  Method 423

389.  Three  Degrees  of  Freedom 426

390.  Geometrical  Construction  for  the  Permanent  Screws 427

391.  Calculation  of  Permanent  Screws  in  a  Three-system 428

392.  Case  of  Two  Degrees  of  Freedom 430

393.  Freedom  of  the  Fourth  Order       . 431

394.  Freedom  of  the   Fifth  and  Sixth  Orders 432

395.  Summary          ...........  432


CHAPTER   XXVI.
AN  INTRODUCTION  TO  THE  THEORY  OF  SCREWS  IN  NON-EUCLIDIAN  SPACE.
