1888. - PREFACE. - The only complete collection of meteorological tables is that of Guyot, first published by the Smithsonian Institution in 1852. This has been enlarged in successive revisions until the 212 pages of the original work have grown to 738 in the fourth edition, forming a very valuable compilation of all the more important meteorological and physical tables in use since 1850. This last edition leaves nothing to be desired from a historical stand-point, but the working meteorologist still lacks a collectio l of the best tables, in compact form, convenient for use, and at small cost. The tables now presented have been in constant use by the author, and their present form is the result of many years experience in the application of various tables. They are published, not to supersede the earlier and more extended collection, but as a , convenient hand-book. In the general plan of the work, the main points to be noted are as follows 1. As far as poseble, all tables relating to the same subject are placed together. 2. All similar tables are united. Thus, the three tables for converting millimetres to inches, on pp. 200, 225 and 258 of Guyotl form Table SXSII of this collection. In addition to compactness and ease of reference, this gives a table for all conversions needed, while previously there has been published no single table that will convert barometrical observations at the highest stations, e. g. Pikes Peak. 3. Only one table is given for each computation. For barometric hypsometry, in place of Guyots seven tables in both English and French measures, only one is given in each, the best and most convenient, as found by six years constant use of various tables. 4. Only tables needed for current meteorological work are included. All references to Guyot are to 4th ed., Wash., 1884. TEXPERATURE TABLES. iv Thus, tables for converting Reaumur temperatures, Russian half lines, etc., are omitted, because needed to-day only for the reduction of old observations, and this rare use can well be supplied by Guyot. 5. The latest determination of the metre is used in all linear tables. The old length of the metre, 39.37079 in., has been used thus far, in all tables in this country and abroad, the usual argument being the inadvisability of a change previous to an authoritative determination. But the length of the metre is now known so closely that the outstanding correction can affect none of the values in our tables while the old length, when the tables are carried to .001 in. Cn6 mm roduces a-error of .001 in. The length adopted is 39.3702 in., for which determination I am indebted to Professor TV A. Rogers, of Bowdoin College, who is-confident that the true value lies between 39.37015 and 39.3702 in. An error of .0001 is hardly possible, and as the change of .0006 from the old value makes a change of only .001 in. in the conversion, it is clear that any possible outstanding error is far within the tabular values. A table computed on the new length will require no modification in the future. G. Several new tables are introduced. At the head of each table, or in its introduction, the authority is stated. If the table be nsw, i. e., recomputed or never before published in this form, it is marked Original if copied or enlarged from Guyot or any other author, the source is kiven. 7. At the end of the volume are given plates showing the distribution of the more important meteorological elements for the United States. I gratefully acknowledge the great assistance rendered me by Mr. C. J. Sawyer in the final arrangement of the hand-book. H. A. HAZEN. WASHINGTON D , . C., August 7, 1888. CONTENTS. TEM EILA T T A U I I L E E S 1 . - 9. I. Co lversiono f rri tlings F . into C.. . . . 11.. . . . ...