The major impact of artificial radioactive material on the oceans has been as a potential pollutant, and, in particular, concern has centred on the public health problems that might arise through human exploitation of marine environments. This public health problem has been an important stimulus to marine pollution methodology. The development and deployment of critical path analysis techniques to the control of this material and to the assessment of its significance for human radiation exposure (Preston 1969; Foster, Ophel and Preston 1971; Slansky 1971) not only exemplifies the control of a chemical pollutant but has served as a stimulus to produce much of the basic physical, chemical and biological data required for its proper implementation. In more recent years the advantages which labelled environments confer for studies of a much wider physical, chemical or biological nature are being increasingly recognised (Natn. Sci. Fdn 1971; Volchok et al. 1971; Lowman, Rice and Richards 1971; Duursma, 1972; Preston, Jefferies and Pentreath 1972,) and many of the tools of nuclear technology, radio-isotopes, reactor propulsion systems, isotope power sources, neutron activation analysis techniques, etc., will enjoy an increasingly important role in oceanography, not only in basic investigations but also in the rational exploitation of marine resources.

‘Science,’ wrote Ernst Cassirer in his Essay on Man, ‘begins with a quest for simplicity.’ Remarkably enough, tradition has preserved the name of the man who first undertook such a quest: the first scientist. He was Thales of Miletus (ca 624–545 b.c.), one of the Seven Wise Men of the ancient world and the founder of the great Ionian school of natural philosophy. He appears to have been the first to have found the courage to abandon traditional mythopoetic explanation and to try and account for natural phenomena in terms of natural forces. As Aristotle, incidentally, the last of the Ionian scientists, put it, Thales was the founder of the philosophy which asserts that ‘the principles which (are) of the nature of matter (are) the only principles of all things’ (Aristotle a).

Oceanography, as is well known, is considered a young science, lacking in old traditions. Nevertheless, the interest in oceans and seas may in some special cases be traced back as far as the centuries before the beginning of the Christian era. Reference may be made, for instance, to the Roman poet Lucretius, who in his work De rerum natura expressed astonishment that the amount of water in the seas does not augment in spite of the fact that the discharge of all the rivers in the world gathers there. Lucretius considered the effect of evaporation a possible explanation for this fact, thus mentioning one of the principal factors which determine the water cycle in nature, at least during periods in which average climatological conditions prevail. During periods characterised by more pronounced climatological deviations the equilibrium of the water cycle may be greatly disturbed. As an interesting example it may be mentioned that during the last glacial period considerable quantities of sea water were transformed into inland ice. It has been estimated that the water level in the oceans and seas at that epoch was approximately 100 metres lower than at the present time.

The first version of the bathythermograph (BT) was invented by Dr A. F. Spilhaus and reported in 1938 (Spilhaus 1938). In response to the wartime need for information useful to sonar, the instrument was improved and manufactured in quantity (Couper and LaFond 1970). Beginning with the pre-war invention, a discussion is presented of the development and use of the BT; its manufacture and testing; the training programme for observers; and collection, processing and use of BT data.

A historical review of the physical and chemical data collected from the Suez Canal waters in the first 40 years (1867–1906) during and after its filling shows that it was the focus of interest of many explorers and scientists. From 27 successive observations (table) the waters were completely analysed seven times. The salinity (density) was measured along the canal on eight occasions, of which four were not previously known. The first observations along the Canal were made in May 1870 by the Admiralty Ship Blue Cross. Her results, together with the second set of observations (February 1872), were found in a small booklet printed in Alexandria (Tissot 1872). The data of two sections (Durand-Claye 1875a; Anonymous 1907) were found by the author as unpublished manuscripts and are revealed here for the first time.

A comment on the determination of salinity of sea water by evaporation to dryness was found in a handwritten manuscript by Durand-Claye (1873). This comment was eliminated in the published text (Durand-Claye 1874), and is reproduced here for its interest to the history of chemical oceanography.

The difficulties in making a comparative study of these old data are explored. It is suggested to start some sort of ‘practical historical oceanography’ by studying old hydrometers, thermometers and other oceanographic apparatus using modern equipments in order to reassess the data of old expeditions.

The tradition of oceanographical research was established in Scotland, more especially in Edinburgh, in the mid-nineteenth century.

The earliest observations to be made in coastal waters in Scotland are attributed to Robert Stevenson when in 1812 he carried out a survey of the Dee at Aberdeen (Stevenson 1872). He found that while there was an outward upper current of fresh water there was also an inward undercurrent of salt water, which gave rise to the tidal rise and fall in the river. This may be the first recorded example of salt-water density wedge penetration into estuarine waters.