58 BULLETIN 139, UNITED STATES NATIONAL MUSEUM 



So far as cfiii be ascertained the Hopi used coal from the near-by veins 

 only for firing pottery. That they secured a high heat is seen by 

 portions of vessels fused in the kiln. This sporadic use of coal is 

 separated by many centuries from the beginning of the employment 

 of this most important fuel by enlightened man. 



Fuel oil. — There is no evidence of the burning of natural mineral 

 oils, tars, and waxes in the domestic economy previous to the age of 

 inventive progress. In lighting there is much information that will 

 be considered at another place. 



Alcohol, gas, gasoline, and electricity. — Note should be taken of the 

 number and value of modern heating materials over those used be- 

 fore the present age; in fact, none of these deviations produced by 

 science came into prominence until late. Until man is enabled to 

 unlock other forces it may be predicted that gas as a heating prod- 

 uct will have the greatest development. 



FIRE IN ARCHEOLOGICAL RESEARCH 



The value of fire evidences in archeological studies has long been 

 recognized. The tantalizing problem of the beginning of the use of 

 fire is always appended to the discoveries of the skeletal and cultural 

 remains of early man. The fact that clay baked by fire retains 

 imperishably the simulacrum of impressed forms is responsible for 

 information of the greatest value as to the works of prehistoric man. 

 In the ruins in the Pueblo region there are often encountered masses 

 of burnt clay which have impressions of the roof beams, poles, or 

 thatching, giving a clear idea as to these details of architecture. 

 The clay masses are part of the exterior covering of roofs, and record 

 the destruction of a house by fire, in which the clay became baked. 

 Charred corn preserving the size and character of the ears are found, 

 also other objects of wood reduced to imperishable charcoal. It is 

 very apparent also that pottery is one of the best conservers of an- 

 cient art. Even the delicate striae of the fingerprints of the ancient 

 artist are preserved. 



In classical archeology the value of fire evidences are similarly 

 important. For instance, the "red burnt brick in Egypt is all Ro- 

 man or Arab; in Greece and Asia Minor, red brick and mortar is 

 Roman, Byzantine, or later." ^® 



SMOKE AND FIRE SIGNALS 



One of the early uses of fire was in signaling. These were day sig- 

 nals by smoke and night signals by bright fire. Incidently, the odor 

 of smoke became a signal or warning of the presence of man. In 

 the course of development, signals which conveyed a few simple ideas 



♦• How to Observe in Archeology, British Musuem, London, 1920, p. 15. 



