Naturally, there exist three kinds of optical beams: parallel, divergent, and convergent (see Fig. 1.1.1). If a beam, either divergent or convergent, has a single point of intersection of all optical rays it is called a homocentric beam (Fig. 1.1.1b,c). An example of a non-homocentric beam is shown in Fig. 1.1.1 d.

an amiable temper

Our senses, our instincts, our intellections are all instruments of adaptation.

Those of us who didn't want OBHWF felt that Rowling was making a mistake, not that she was being misleading.