RURAL ENGINEERING. 585 



RURAL ENGINEERING. 



Boad materials of southern and eastern Maine, II. Leighton and E. S. 

 H.v.sriN (U. S. Dc])t. Ayr., Office I'lib. RuuiIh Hid. ,i,i, />/>. 56, ph. 3, iiuij) 1). — 

 This bulletin, prepared in cooperation between the U. S. Geological Survey, tlio 

 State Survey Coniniission of Maine, and the OtHce of Public Roads, is the tirst 

 of a series bavinj:; in view tlie description, location, and testini^ of available 

 road materials in the different States. 



In .Maine the area report«'d upon did not include the northern part because 

 of its sparse pitpuiation and the relative unimportance of the road proldeni. 

 The principal source of road material in the area reported upon is stated to be 

 the gravels, but owing to their great abundance and irregular distribution an 

 extensive study of these could not be included except in those cases where 

 detailed studies have already been made. The bulletin is especially devoted 

 to rnad materials located near the liirge cities and to deposits favorably situated 

 as regards shipment. 



After a brief discussion of the general geology of the section and an outline 

 uf the methods u.»<ed in testing the various si)ecimens of rocks, the materials 

 are described and discussed, grouped (1) according to variety and (2 1 accord- 

 ing to localities with the varieties connnon to each. 



Specifications and notes on macadam road construction, A. X. .Joiixso.x 

 (IJiKjin. \cics, GO {I'.lOU), No. 10, pp. Jf89-.'i92). — This is a paper read before the 

 Western Society of Engineers, October 21, 1908. 



The author, who is Illinois State highway engineer, expresses radical views 

 on the construction of macadam roads, chief among which is that of using the 

 large-sized stone for a wearing surface. He recommends that the tirst course 

 of macadam should consist of broken stone from i to li in. in size, thoroughly 

 raked and harrowed so that all the small iiarticles will reach the bottom, be- 

 cause, since this is the state of stable eiiuilibrium, the roller will compact it 

 more readily. Also, in badly drained roads, if the smallest pieces are at the 

 bottom the ground surface is less likely to be disturbed when the frost conies 

 out of the gronn<l. He believes there is no valid reason for bonding the lower 

 roiirse, but it should be thoroughly and slowly rolled to lock the pieces together. 

 If the voids are tilled with tine material this locking can not be obtained. 



The second course should consist of a layer of li to 3-in. stone having a Duval 

 coetlicient of wear of not less than 1.1, because this size will lock more firmly 

 than a 1-in. and make the surface more resistant. The layer when consoli- 

 dated should be 2 in. for a fJ-in. road, or 4 in. for a 10-iu. road. The larger the 

 ex|K»se<l pieces the greater will be the resistance to wear. Although the bot- 

 tom liiyer may be of any kind of nonabsorbent. endiiring material, the se<*ond 

 layer should l)e more carefully selected. 



Tile third course should consist of rock screenings containing all the dust, 

 the sizes of these being from A to 1 in., govenunl by the softness of the material. 

 The s<-re«Miiiigs should be wet and rolled, and the second course so thoroughly 

 rollc*! before screenings are placed on it that travel will not disitlace the i>ieces 

 enough to allow the latter to pass through. In this paper the author observes 

 that "the first place to give has been where there evidently 1ms been a cluster 

 of fine particles." 



Macadam roads, A. 15. Ki.KTCiiiiR iU. N. Ifrpt. Apr., Fannrrs' It ill. ,i.iS. pp. 3!), 

 flux. /").— This is a condensed and revised eilitioii of HuUetin 2!t. Otiice of rub- 

 lie Uoads ( E. S. K., 1!>, p. .'JSC). It (h'scribes in some detail the essential fea- 

 tures of the best practice of niMcadiini mad construction in rural se<-tions with 

 "lata as ft) costs. Standard details of construction used bv the .M.issaihusetts 



