PUBLISHER'S PREFACE 



T was the original plan of the author to have 

 used as a frontispiece in this work a portrait 

 of Mr. D. W. Coquillett, who discovered the 

 economic value of hydrocyanic acid gas as an 

 insecticide. Mr. Coquillett prefers to be remembered 

 by the discovery he made in his experimental and prac- 

 tical work with hydrocyanic acid gas. The publishers 

 therefore take pleasure in introducing this volume 

 with a portrait of the author, who has done so much 

 to utilize in a practical way the discovery made by Mr. 



Coquillett. 



ORANGE JUDD COMPANY. 



