Notes on the Works of Soioing, Sfc. 
435 
little or no oxide of iron and alumina than in others containing 
a good deal of iron or alumina. The percentage of fluoride of 
calcium which accompanies most phosphatic minerals likewise 
affects their commercial value ; and in a minor degree their 
value is further affected by their porosity or density, and the 
facility with which they can be reduced to a fine powder. 
Laboratm-y, 11, Salisbury-square, Fleet-street, E.C., 
July, 1875. 
XVII. — Notes on the Works of Sowinr/ and Consolidation of the 
Dunes or Coast Sand-hills of Gascony, containing information 
obtained from M. A. Cherot, a French Economist, with a view 
to the introduction of similar loorks on the Sand-drifts that are 
rapidly advancing over and threatening eventually to destroy 
the City of Beiriit. Communicated by General F. CoTTON, 
C.S.I. 
The sand-hills which run along the shores of the Gulf of 
Gascony, and which have been fixed by the process of Bre- 
montier, extend from north to south from the mouth of the 
Garonne to the mouth of the Adour, having a length of nearly 
120 miles and a mean breadth of 3 miles. 
Before they were fixed by the plantations which have been 
recently made, they advanced each year toward the interior. 
No effectual obstacle to their encroachment having been found, 
they covered all the buildings lying in their path ; and had 
buried up to the belfry the old church at Soulac, when Bremontier 
undertook to fix these masses of sand, and to arrest their progress 
into the interior of the country. 
The essential part of the system adopted consisted in sowing 
the dunes with pine-seed ; but as the sands were displaced every 
day by the winds of the coast, it was necessary, to ensure a suc- 
cessful sowing, to employ certain means invented by Bremontier, 
without which no vegetation could have obtained a hold upon 
these moving masses. 
These precautions are shown in a detailed and exact manner 
in the annexed Specification. 
The sowing, as appears in the Specification, is usually made 
with a mixture of the seeds of the pine and of the broom-plant. 
The broom comes up first, and, before the protection of 
the branches (brushwood) has ceased to be efficacious, it covers- 
