August 31, 1883.] 



SCIENCE. 



261 



spiral course, as already explained, assists some- 

 what to overcome this ; but it is mostly reme- 

 died by the builder, as each round is made, 

 trimming down the up-hill part of the course 

 to about half, until, by the time tlie blocks are 

 leaning considerably, "the course is level (leav- 

 ing out the spiral inclination). 



As each block is being fitted, it is held near 

 its intended position by the left hand of the 

 builder, who at one stroke cuts off the triangle 

 on the right edge, giving a trapezoidal form. 

 The left edge of the preceding block receives tlie 

 same treatment, and the block is shoved into 

 place. Tlie snow-knife is rapidly passed back- 

 wards and forwards in the joints at the side 

 and bottom, cutting off all inequalities, and 

 making a fine powdery snow, which acts as a 

 binding mortar. The last act is to give the 

 block a sharp shoving blow with the open 

 hand from the top, and another from tlie left 

 side, which firmly sets it in place. The blocks 

 all laid, the igloo is now complete, except the 

 ' chinking ' of the joints to render it air-tight, 

 there being many large crevices. The clunk- 

 ing of an igloo is a very ingenious atKiir ; 

 the material being cut diagouallj- from the 



lower edge of the upper block on the horizon- 

 tal joints, and from the left edge of the right 

 block on the vertical ones, if the person be 



^c/f hanct 



ciinched. 



VERTICAL CttOas-SECTION TIinOUOQ 



right-handed. As the knife in the right hand 

 thus trims the edges, the left fist, tightly 

 clinched, follows the knife, and rams the cut 

 portion tightly into the crevice, rendering it 



