In a few pages I would like to express and to justify my admiration for the exceptional book of Jeffrey Barash. His training as an his torian, complemented by that of the philosopher, has served him richly, not only in the discovery of rare texts and of unpublished correspondence but in the reconstruction of the philosophical landscape at the beginning of the century, and then in the period between the two wars. Standing out in the foreground of this land scape are the two mountains constituted by Sein und Zeit and Hei degger's work following the Kehre. This reconstruction by no means intends to establish 'influences' in the mediocre, mechanis tic sense, but rather subterranean continuities between Heidegger's work and his intellectual environment in order to enhance, by the effect of their contrast, the specific intelligibility of this work. In order to appreciate the consequences of continuity as well as of discontinuity, it was necessary to identify and to emphasize a touchstone-question, endowed with the quality of great per durability, and to summon before it all of the protagonists, in cluding Heidegger himself, in an intellectual combat dating back nearly a hundred years. Announced in the title of the work, this question concerns historical meaning. By this term the author wanted to designate the stubborn ques tion, most exactly approximated by the term coherence in its ap plication to history."

In a few pages I would like to express and to justify my admiration for the exceptional book of Jeffrey Barash. His training as an his torian, complemented by that of the philosopher, has served him richly, not only in the discovery of rare texts and of unpublished correspondence but in the reconstruction of the philosophical landscape at the beginning of the century, and then in the period between the two wars. Standing out in the foreground of this land scape are the two mountains constituted by Sein und Zeit and Hei degger's work following the Kehre. This reconstruction by no means intends to establish 'influences' in the mediocre, mechanis tic sense, but rather subterranean continuities between Heidegger's work and his intellectual environment in order to enhance, by the effect of their contrast, the specific intelligibility of this work. In order to appreciate the consequences of continuity as well as of discontinuity, it was necessary to identify and to emphasize a touchstone-question, endowed with the quality of great per durability, and to summon before it all of the protagonists, in cluding Heidegger himself, in an intellectual combat dating back nearly a hundred years. Announced in the title of the work, this question concerns historical meaning. By this term the author wanted to designate the stubborn ques tion, most exactly approximated by the term coherence in its ap plication to history.

X-ray and neutron crystallography have played an increasingly impor tant role in the chemical and biochemical sciences over the past fifty years. The principal obstacles in this methodology, the phase problem and com puting, have been overcome. The former by the methods developed in the 1960's and just recognised by the 1985 Chemistry Nobel Prize award to Karle and Hauptman, the latter by the dramatic advances that have taken place in computer technology in the past twenty years. Within the last decade, two new radiation sources have been added to the crystallographer's tools. One is synchrotron X-rays and the other is spallation neutrons. Both have much more powerful fluxes than the pre vious sources and they are pulsed rather than continuos. New techniques are necessary to fully exploit the intense continuos radiation spectrum and its pulsed property. Both radiations are only available from particular National Laboratories on a guest-user basis for scientists outside these Na tional Laboratories. Hitherto, the major emphasis on the use of these facilities has been in solid-state physics, and the material, engineering and biological sciences. We believe that there is equivalent potential to applications which are pri marily chemical or biochemical."

Travelling wave processes and wave motion are of great importance in many areas of mechanics, and nonlinearity also plays a decisive role there. The basic mathematical models in this area involve nonlinear partial differential equations, and predictability of behaviour of wave phenomena is of great importance. Beside fluid dynamics and gas dynamics, which have long been the traditional nonlinear scienes, solid mechanics is now taking an ever increasing account of nonlinear effects. Apart from plasticity and fracture mechanics, nonlinear elastic waves have been shown to be of great importance in many areas, such as the study of impact, nondestructive testing and seismology. These lectures offer a thorough account of the fundamental theory of nonlinear deformation waves, and in the process offer an up to date account of the current state of research in the theory and practice of nonlinear waves in solids.

This book is intended as an easy to read supplement to the often brief descriptions of hydrogen bonding found in most undergraduate chemistry and molecular biology textbooks. It describes and discusses current ideas concerning hydrogen bonds ranging from the very strong to the very weak, with introductions to the experimental and theoretical methods involved.