PREFACE TO ORIGINAL EDITION.
I have to acknowledge the kind aid which I have received in the preparation of this book.
Mr. Nasmyth has permitted me to use some of the beautiful drawings of the Moon, which have appeared in the well-known work published by him in conjunction with Mr. Carpenter. To this source I am indebted for Plates VII., VIII., IX., X., and Figs. 28, 29, 30.
Professor Pickering has allowed me to copy some of the drawings made at Harvard College Observatory by Mr. Trouvelot, and I have availed myself of his kindness for Plates I., IV., XII., XV.
I am indebted to Professor Langley for Plate II., to Mr. De la Rue for Plates III. and XIV., to Mr. T.E. Key for Plate XVII., to Professor Schiaparelli for Plate XVIII., to the late Professor C. Piazzi Smyth for Fig. 100, to Mr. Chambers for Fig. 7, which has been borrowed from his "Handbook of Descriptive Astronomy," to Dr. Stoney for Fig. 78, and to Dr. Copeland and Dr. Dreyer for Fig. 72. I have to acknowledge the valuable assistance derived from Professor Newcomb's "Popular Astronomy," and Professor Young's "Sun." In revising the volume I have had the kind aid of the Rev. Maxwell Close.
I have also to thank Dr. Copeland and Mr. Steele for their kindness in reading through the entire proofs; while I have also occasionally availed myself of the help of Mr. Cathcart.
ROBERT S. BALL.
Observatory, Dunsink, Co. Dublin.
12th May, 1886.