EarthRef.org Digital Archive (ERDA) -- Sur L'intensite de champ magnetique terrestre dans le passe historique et geologique

Description
Archeo or paleomagnetical studies are devoted generally to the direction of the ancient (magnetic) field ; the present paper deals with the intensity of this field. Successive phases of the method which the authors have developed since 1937 for this purpose are exposed, followed by a general perspective of its results. The paper can be divided in two parts, each one including three chapters.

In the first part, after a brief summing up of the basic facts, the few tentatives which have been put into action in order to find the intensity of the ancient field are examined. Then the method proper to the authors and which consists in comparing thermoremanent magnetizations artificially given to a sample, with the one that the same sample presented in nature when it had been found, are described. Systematic series of trials are necessary in order to be able to eliminate, one by one, the numerous defects which prevent of making a safe use of the method in its simplest form. Some results are incidently brought out regarding the last past centuries.