This is the third volume of the collection of new devices, modifications of existing equipment, and other items of interest of this nature published in the journal Applied Spectroscopy. These tricks have proved of value since they first appeared in the journal in 1959. They give solutions to many problems of workers in the var­ ious fields of spectroscopy. For the novice, the use of ali three vol­ umes may provide insight into the improvements that have been made in the instruments and techniques that he is currently using. The novice may be saved the necessity of discovering some shortcut that many experienced spectroscopists are already using. The contributions in this third volume are selected from the years 1970 through 1973. The subject arrangement is the same as in Volumes 1 and 2 according to the area of spectroscopy. Those tricks concerned with the same device are placed together so that the reader can easily compare them. To maintain the advantages in­ herent in a single collection of contributions, the subject index for this volume is cumulative including the tricks in the previous vol­ umes. Both author and journal indices are provided for this vol­ ume, the latter citing the original Applied Spectroscopy citation. The use of the contributions has been approved by the So­ ciety for Applied Spectroscopy, whose cooperation in this matter is gratefully acknowledged.