The Lucidator is a miniature, dual-scale computer for attaching to the car key-ring. From it journey times, average speed, fuel consumption, conversion of m.p.h. to k.p.h., kilometres to miles. kg./sq. cm. to lb./sq. in.. and vice versa, and many other calculations are possible without recourse to mental or finger arithmetic. The circular calculator has a leather case and is accompanied by a paper wallet of instructions. Made by Lucidator Ltd., 7, Birchin Lane, E.C.3, it is rather high-priced, at 10s. 6d., but should prove useful during the continental tour to those bad at sums.