The operations of elementary algebra are of finite character; that is to say, an algebraic expression depends, explicitly or implicitly, only on a finite number of variables. The step from algebra to analysis is taken when we begin to consider expressions depending on an infinite number of variables; for instance, the limit of a sequence (an) depends on the infinite set of variables a1, a2, …. Such an infinite set of variables is most conveniently thought of as the set of values of a function; thus the sequence (an) is a function of the positive integral variable n, the single term a3, for example, being the value of the function when n is given the particular value 3. Thus the characteristic features of analysis are (i) the systematic use of functions of a variable capable of an infinity of distinct values, and (ii) the consideration of expressions that involve the values of such a function for an infinity of values of the independent variable.

Nearly two years ago I was given permission to form a School Mathematical Society, hoping thereby to create a live interest in mathematics and to show that there is a limitless treasure untouched by the demands of the academic courses of the School Certificates. Naturally topics have to be chosen which require little more than a knowledge of School Certificate and Higher School Certificate mathematics, and the Mathematical Society has been limited, at the present, to the Fifth and Sixth forms.

The four star polyhedra discussed on pp. 171-173 of Lines’ Solid Geometry form an interesting series of constructions based on the angle of 72° The finished products form fine decorations for the mathematics laboratory, as well as visual aids.

The mathematical theory of rocket motion has been given by Rosser, Newton and Gross (1947) for the case of unrotated, and slowly rotated, rockets. A rigorous treatment of the subject has been given also by Rankin (1949) in a recent paper which is applicable to both unrotated and rotated rockets.

One of the main objects of such work is the derivation of formulae which may be used to predict the behaviour of the rocket under the action of various disturbing influences. Thus, an angular deviation of the rocket from its normal trajectory may be caused by the thrust not passing through the centre of gravity, by the action of a crosswind (usually assumed constant in the theory), or by the rocket being launched with an initial yaw or initial angular velocity about an axis at right angles to the rocket axis. Malaligned fins may also cause such a deviation.