206 [ASSEMBLT 



thickness of stratified stone, especially sandstone, entirely uniform 

 and homogeneous in texture, or without interlainination of shaly 

 matter, it follows that by turniui^ tiie blocks upon their ed<:^es, we 

 shall in one case have the face of a harder or coarser layer, and in 

 another of a softer layer of the same rock, thus exposing the wall to 

 unequal weathering. Not unfrecpiently the face of the stone is the 

 line of the soft shaly parting, and the effects of this practice may 

 often be seen in the scaling off of an entire surface of a block of 

 ashlar for several square feet in extent. Such examples may be seen 

 in some of our buildings, which have been erected within the past- 

 twenty-five years. Had these blocks been laid in an opposite direc- 

 tion, the edges of the shaly seams only would have been exposed, 

 and their destruction would have been comparatively slow. The 

 sandstones separate usually with great freedom along the line of 

 bedding, and thus offer great facilities for dressing the surface in the 

 direction of the laminae ; and from this cause, and the desire to pre- 

 sent as large a surface as practicable in each block, has arisen the 

 practice of setting them upon their edges. A block of stone may, 

 however, be split in the same direction, through one of its more 

 sandy layers, and the objections urged may not be so palpable. 



Ail equally reprehensible practice is the cutting of step-stones 

 from blocks with distinct shaly partings, which produce exfoliation- 

 and consequent inequality of the surface. 



Mode of Dressing. 



In the nse of argillaceous sandstones, as well as some other rocks, 

 there are some considerations as to the mode of dressing which 

 should not be forgotten. There are some stones which, if dre?sed 

 elaborately, disintegrate rapidly upon the surface. This comes from 

 the crushing of the material under the tool;* the natural texture 

 and cohesion of the particles being thus broken up, it absorbs more 

 water, and on freezing, decays rapidly and becomes unsightly. Many 

 stones that are unfit for finely dressed work are nevertheless quite 

 durable if rough dressed ; that is, by dressing the joints close and a 

 smooth space along the edge, while a greater part of the face is left 

 roughly broken without tool-work of any kind. During wet weather, 

 the moisture will collect at the numerous projecting points or edges, 

 and much of it drops off which will be absorbed by a smooth dressed 

 face of stone. The effect of freezing is much less destructive under 

 such conditions. Moreover, a moderate degree of weather-wearing 

 on such surfaces is less conspicuous than on finely dressed stone. 

 The dressing of the stone in the [University buildings at Ithaca is a 

 'good example of this kind of work, 



* The term deadening of the surface is used by the workmen to designate this condition.. 



