EDUCATIONAL BOOKS. 



Airy, G. B. continued. 



UNDULATORY THEORY OF OPTICS. Designed for the Use of 

 Students in the University. New Edition. Crown 8vo. cloth. 

 6s. 6d. 



The undulatory theory of optics is presented to the reader as having the 

 same claims to his attention as the theory of gravitation : namely, that it is 

 certainly true, and that, by mathematical operations of general elegance, it 

 leads to results of great interest. This theory explains with accuracy a 

 vast variety of phenomena of the most complicated kind. The plan of this 

 tract has been to include those phenomena only which admit of calculation, 

 and the investigations are applied only to phenomena which actually have 

 been observed. 



ON SOUND AND ATMOSPHERIC VIBRATIONS. With the 

 Mathematical Elements of Music. Designed for the Use of Students 

 of the University. Crown 8vo. 9^. 



This volume consists of sections, which again are divided into numbered 

 articles, on the following topics : General recognition of the air as the 

 medium which conveys sound ; Properties of the air on which the forma- 

 tion and transmission of sound depend; Theory of undulations as applied 

 to sound, &>c. ; Investigation of the motion of a wave of air through the 

 atmosphere ; Transmission of waves of soniferous vibrations through dif- 

 ferent gases, solids, and fluids ; Experiments on the velocity of sound, 

 &*c. ; On musical sounds, and the manner of producing them ; On the 

 elements of musical harmony and melody, and of simple musical composi- 

 tion ; On instrumental music; On the human organs of speech and 

 hearing. 



Bayma. THE ELEMENTS OF MOLECULAR MECHA- 

 NICS. By JOSEPH BAYMA, S. J., Professor of Philosophy, 

 Stonyhurst College. Demy 8vo. cloth. JOT. 6d. 

 Of the twelve Books into -which the present treatise is divided, the first 

 and second give the demonstration of the principles which bear directly on 

 the constitution and the properties of matter. The next three books contain 

 a series of theorems and of problems on the laws of motion of elementary 

 substances. In the sixth and seventh, the mechanical constitution of mole- 



