s 



f: 



Copyright© 1951 by 

 Cranbrook Institute of Science 

 Bulletin No. 31 



Copyright© 1962 by 

 G. W. Prescott 



ISBN 0-697-04552-8 



Library of Congress Catalog Card Number: 61 — 18674 



All rights reserved. No part of this book may be 

 reproduced in any form or by any process without 

 permission in writing from the copyright owner. 



Fourth Printing, 1970 



Printed in the United States of America 



