rably　taken　off。〃

Pressure　seems　to　have　played　a　considerable　part　in　the　formation　of　carboniferous　strata。 In　fact；　it　is　to　its　degree　of　power　that　are　due　the　different　sorts　of　coal；　of　which　industry　makes　use。　Thus　in　the　lowest　layers　of　the　coal　ground　appears　the　anthracite；　which；　being　almost　destitute　of　volatile　matter；　contains　the　greatest　quantity　of　carbon。 In　the　higher　beds　are　found；　on　the　contrary；　lignite　and　fossil　wood；　substances　in　which　the　quantity　of　carbon　is　infinitely　less。 Between　these　two　beds；　according　to　the　degree　of　pressure　to　which　they　have　been　subjected；　are　found　veins　of　graphite　and　rich　or　poor　coal。 It　may　be　asserted　that　it　is　for　want　of　sufficient　pressure　that　beds　of　peaty　bog　have　not　been　pletely　changed　into　coal。 So　then；　the　origin　of　coal　mines；　in　whatever　part　of　the　globe　they　have　been　discovered；　is　this：　the　absorption　through　the　terrestrial　crust　of　the　great　forests　of　the　geological　period；　then；　the　mineralization　of　the　vegetables　obtained　in　the　course　of　time；　under　the　influence　of　pressure　and　heat；　and　under　the　action　of　carbonic　acid。

Now；　at　the　time　when　the　events　related　in　this　story　took　place；　some　of　the　most　important　mines　of　the　Scottish　coal　beds　had　been　exhausted　by　too　rapid　working。 In　the　region　which　extends　between　Edinburgh　and　Glasgow；　for　a　distance　of　ten　or　twelve　miles；　lay　the　Aberfoyle　colliery；　of　which　the　engineer；　James　Starr；　had　so　long

directed　the　works。 For　ten　years　these　mines　had　been　abandoned。　No　new　seams　had　been　discovered；　although　the　soundings　had　been　carried　to　a　depth　of　fifteen　hundred　or　even　of　two　thousand　feet；　and　when　James　Starr　had　retired；　it　was　with　the　full　conviction　that　even　the　smallest　vein　h