660 T. T. QUIRKE BOUDINAGE, AN UNUSUAL PHENOMENON 



ics of the deformation of the earth's crust that it is desirable that every 

 type of structure should be made familiar to all who are interested. One 

 of the purposes of International Congresses is to offer to the geologists 

 of the world a convenient opportunity of visiting the peculiar or other- 

 wise noteworthy phenomena of the country which is acting as host. 

 Boudinage is one of those things, visited during the International Con- 

 gress of 1922, which geologists may see in Belgium, although probably 

 not known anywhere else in the world. In spite of the rarity of boudi- 

 nages, they illustrate what a part of the earth's crust has done under 

 particular circumstances and what other parts are likely to do under 

 similar conditions, and their occurrence serves to point a warning to those 

 undertaking mechanical experiments in structural geology. They em- 

 phasize the oft-repeated reminder that the earth's crust is not a uniform 

 member, nor rigid, and that it is in no sense susceptible to theoretical 

 treatment as though it were a member of uniform material and simple 

 structure. 



There seems to be nothing in the arts or in nature which can be com- 

 pared in mechanical origin to boudinages, which makes them the more 

 interesting and the more worthy of study. It is hoped that we shall learn 

 more about them through the researches of our Belgian colleagues. 



