The British Geological Survey holds the most extensive gravity and magnetic databases for the UK and surrounding regions. Until recently these data have only been publicly available through a series of coloured maps and papers published in the scientific literature. These CD-ROMs go a step further by combining maps with new text, based on published research. England, Wales and Scotland are divided into four areas and these two CDs are the first in the series. At present there does not appear to be a plan to cover Northern Ireland. The packaging states that the disks are designed to run on a PC running Internet Explorer® and that there may be problems viewing some of the content on other platforms. However, I did not experience any difficulties viewing both CDs on a Mac running OSX and Safari® other than the disks did not auto-run. I did not try the disks on a Linux platform.

I found the disks easy to navigate, once I got used to the navigation/contents bar being located at the bottom of the page. The contents are broken down into a format similar to a book, except that, as should be expected, hyperlinks enable navigation between sections. The navigation bar provides additional functionality by providing direct links to main sections in the contents including the index. The main ‘Images’ page provides links to map displays illuminated from different discrete directions and a greyscale image with a ‘rotating sun’ enabling some of the data to be viewed with the illumination from any direction. The text is succinct and clearly written, and in the case of the interpretations is up to date with extensive referencing of current work. The illustrations are produced at high resolution and are in colour or greyscale as appropriate. The results of both 2.5-D and 3-D modelling of the subsurface structure from the potential field data are included, much of which is previously unpublished. In each case the methodology is clearly described and any limitations noted. In particular there are some excellent gradient and Euler deconvolution maps that should prove very useful for teaching or to anyone looking for an overview of the subsurface structure as interpreted from potential field data.

The content of the two disks is slightly different. To anyone looking at the disks in isolation this would not matter but the disk for Southern Scotland and Northern England contains more functionality and a wider range of maps than that for Southern England. In particular there is a nice menu for selecting Euler deconvolution maps in the Southern Scotland and Northern England disk that is not on the other. It might be argued that the additional maps are not necessary for Southern England but it does mean that comparing adjacent areas or the continuity of features between areas is not always possible in these displays. It also suggests that the BGS does not intend to release a single guide to the whole of the UK, which in my opinion would be more useful.

The more I look at these disks the more I keep finding. They are very well produced and at £25 each represent good value for money considering the amount of information they contain. I can see they will be very useful in teaching general geophysics and provide nice illustrative examples for more specialized courses in interpretation of gravity and magnetic data. They will also form a good basic reference and supporting map information for research purposes. Highly recommended.