Page:Popular Science Monthly Volume 5.djvu/515

Rh  W. C. Richards, Ph.D., who, having retired from the public lecture-field, offers for sale his extensive collection of instruments. The stock includes duplicates of important pieces, such as coils, batteries, spectroscopes, vacuum-tubes; and it offers an excellent chance for colleges, high-schools, and private students, to supply themselves from this collection. Those who are in want of such instruments should send to Professor Richards for his catalogue.



volume of 263 pages is No. 255 of the publications of the Smithsonian Institution, and it is yet another evidence of the care and thought bestowed by the venerable Secretary of that Institution upon all means and aids suitable for the advancement of human knowledge.

It is Part I. of a series which is to contain the Constants of Nature, tabulated in such a way as to be immediately available for the uses of scientific men, as well as for general reference.

A careful examination of its general plan shows that this work has been admirably done by Prof. Clarke (now of Howard University, Washington). The work can be consulted with great convenience by means of the very complete Index, and on turning to any page the information is found in five columns side by side. The first column contains the name of the substance, as, for example, Iodine; in this column also the letter l or s shows that the substance has been examined in a liquid or a solid state.

The third column contains the specific-gravity determinations which have been made, accompanied by figures showing the temperature at which they were made, and a reference number to each line indicates the authority (volume and page usually) from which the datum is selected. Another symbol in this column, "m. of 6," for example, shows that the determination was the mean of six determinations.

The next column gives the boiling-point in degrees Fahrenheit, together with the height of the barometer at which this element was determined, and the fifth column gives the melting-point.

Sulphur has thirty-two lines devoted to its properties; Tin has eighteen; Bismuth eighteen, etc.

As an example, we extract line No. 7 of Sulphuric Acid. The No. 7 refers us to a paper by H. L. Buff in the "Annals of Chemistry and Pharmacy," fourth supplement (1865-'66), p. 129, and also to various articles quoted in that paper. The line reads: "Sulphuric Acid; SO 3; 1.81958, 47°; 46° to 47° 760m.m.; rs. 25°;" which shows that the specific gravity was determined at 47° Fahr. to be 1.81958, that at 760 m.m., the boiling-point was from 46° to 47° Fahr., and that this specimen resolidified at 25° Fahr.

It only remains to add from Prof. Clarke's modest preface, that the work, "exclusive of its supplement, contains the specific gravities of 2,263 substances, and over 5,000 determinations in all. There are over 2,000 determinations of boiling-point, representing 1,205 different substances; and nearly 500 of melting-point for 326 different substances. In all, the names of 2,572 distinct bodies will be found in the table."

Too few books have honest titles, for these are as often chosen to mislead as to instruct. The present is among those that are accurately described by their names. For, while there is a great deal of interesting scientific physiology in this volume, its distinctive character is that it furnishes physiological knowledge that can be continually applied to practical use. Dr. Hinton, the editor, is an eminent aural surgeon of London, and contributes the article to this volume on "The Faculty of Hearing." We published a portion of that article some time ago in the, and all who read it will attest that it was one of the best practical presentations of the subject that has yet 