Cambridge is honoured this year by its selection for the first meeting held in England by the International Congress of Mathematicians. The Cambridge School has played a notable part in the development of mathematics in Britain, and it may be of interest if I briefly summarize the leading facts of its history, which is indeed closely connected with that of the University. The School is of more than respectable antiquity and inevitably it has been sometimes flourishing and sometimes the reverse. Here I desire rather to bring out the salient features in its history than to discuss details or individual achievements.

When the Mathematical Gazette was founded, statisticians were mainly concerned with the collection and presentation of data. The mathematical side consisted mainly of developments from the work of Gauss and Laplace in the early part of the 19th century, though some surprisingly modern work was done by Edgeworth towards the close of the century. 1889 saw the publication of Galton’s Natural Inheritance, introducing correlation and regression. These two workers influenced Karl Pearson who, in 1900, began the modern era of mathematical statistics with the concept of the significance test usually known by the symbol he used, chi-squared.

Individuals who excel in mathematics have always enjoyed a well deserved high reputation. Nevertheless, a few hundred years back, as an honourable occupation with means to social advancement, such an individual would need a patron in order to sustain the creative activities over a long period. Leonhard Euler (1707-1783) had the fortune of being supported successively by Peter the Great (1672-1725), Frederich the Great (1712-1786) and the Great Empress Catherine (1729-1791), enabling him to become the leading mathematician who dominated much of the eighteenth century. In this note celebrating his tercentenary, I shall mention his work in number theory which extended over some fifty years. Although it makes up only a small part of his immense scientific output (it occupies only four volumes out of more than seventy of his complete work) it is mostly through his research in number theory that he will be remembered as a mathematician, and it is clear that arithmetic gave him the most satisfaction and also much frustration. Gazette readers will be familiar with many of his results which are very well explained in H. Davenport's famous text [1], and those who want to know more about the historic background, together with the rest of the subject matter itself, should consult A. Weil's definitive scholarly work [2], on which much of what I write is based. Some of the topics being mentioned here are also set out in Euler's own Introductio in analysin infinitorum (1748), which has now been translated into English [3].

We discuss the deduction of real euclidean theorems from complex projective theorems, and the reverse process: when is it permissible, in proving a complex projective theorem, to project two given points into the circular points at infinity and use real euclidean methods? We emphasise the difference between the real and the complex, and the consequences of using real numbers to define euclidean geometry, and complex numbers to define projective geometry.

Matrix models are used extensively in demography and population biology. The example discussed here shows how a simple 2 × 2 matrix may prove of use in the study of bird populations. Teachers may find it an interesting illustration of the application of matrices. The knowledge of matrices that is required to appreciate the model and investigate it numerically may be summarised as (1) the expression of two linear equations as a matrix equation, (2) the multiplication of matrices. A deeper understanding of the behaviour of the model comes from the use of eigenvalues.

The interest of pure mathematicians is nowadays shifting from the study of special functions to general function theory. In fact the study of special functions might ultimately be forsaken, as for example in geometry the study of the triangle is now virtually a closed chapter, were it not for one important consideration. That is, that these functions must always be in constant use in mathematical physics. Hence their properties tend to become questions of practical application rather than of theoretical interest. It follows that there is a demand for some method, even if only a formal one, which will derive the required properties in an expeditious manner, without always calling for the services of the professional pure mathematician.

Tonight I shall deal with some examples of mathematical reasoning which have in common only one feature: that of being surprising, or, even, of once having been surprising. We may picture them as monsters, waiting to leap on our loose ideas about mathematics and to tear them to shreds.

I shall not concern ourselves with elementary errors. Every one of you, no doubt, can “prove” that all triangles are isosceles, and that 2 = 1 by simple algebra.

In a recent article (this Gazette, 65 (1981), 87-92) Dr Anderson raised the question of the derivation of the well-known formula for the sum of integer squares, in contradistinction to its mere verification by induction. Some time ago, in response to a request from a colleague, I derived each of the well-known formulas

by arguments based upon the decomposition of rectangles. As a complement to Dr Anderson’s article, these may be of interest; especially, in view of the derivation, to those requiring the formulas for elementary integration from first principles.