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The research into the secular variation of the geomagnetic field, which enables the gradual explanation of the origin and maintainance of the field, has been carried out by methods of direct observations over the past 500 years, and by palaeomagnetic investigation of rocks giving approximate information on the character of the geomagnetic field at the time of the inception of the various geological formations. Research into the geomagnetic field in the socalled historical era, which is in fact an intermediate between palaeomagnetic research into the field in geological epochs and present day observations, comes under the heading of archaeomagnetism. It enables a certain elucidation of the dynamics of the field in a period covering several thousand or tens of thousand years. Numerous archaeological discoveries on Czechoslovakian territory support the evidence that praehistoric people inhabited these regions continuously for a considerable period. This provides fertile ground for archaeomagnetic research. Several archaeologically dated sites were chosen for the first investigations of this kind, some of which were dated also with the help of the C 14 radioactive method. These sites cover the period from 4400 B. C. to the present. Samples were mostly gathered from furnaces and fireplaces in the vicinity of inhabited areas. The investigation concentrated on determining the total geomagnetic field intensity F. The successive double-heating method of E. Thellier (1959) has been used. Results of laboratory measurements of samples from Bylany divided according to their age and covering the period between 4400 and 3000 B. C. with steps of 200 to 300 years between the various samples, are shown in Fig. l. to 3. The curves of the first two samples (dating back to 4400 B. C.) show that the demagnetization and magnetization processes are of a similar character. The demagnetization curve at first shows a gradual decrease as far as 400C, but for higher temperatures the magnetization decreases mush faster. Similarly the magnetization curve shows a considerable enhancement above 400C. The mean coefficint k, defining the ratio between the original field and the laboratory field is equal to 0. 8, and after correction with respect to a laboratory field equal to the present geomagnetic field 0. 94. The sample (4100 B. C.) (Fig. 1.) shows k=0. 86 after correction a being the demagnetization curve, b the magnetization and c the "mirrored" curve. The third group of samples (3600 B. C.) has k=0. 46 for three samples. The curves for one of these samples are shown in Fig. 2. For another sample (3300 B. C.) k=0. 58. The last group of samples from Bylany (dating back to 3000 B. C.) is represented by the samples with k=0. 85 (Fig. 3.). Further the demagnetization and magnetization curves of some samples from the site near Mohelnice were investigated. The site dates to 3600 to 3000 B. C. The values Ir for van-

Results of Archaeomagnetic Research in Czechoslovakia for the Epoch from 4400 B. C. to the Present