vidently　due　to　a　physical　cause；　〃My　lad；〃　the　old　man　would　say；　〃we　must　wait。　It　will　all　be　explained　some　day。〃

However；　it　must　be　observed　that；　hitherto；　neither　Harry　nor　his　father　had　ever　been　exposed　to　any　act　of　violence。　If　the　stone　which　had　fallen　at　the　feet　of　James　Starr　had　been　thrown　by　the　hand　of　some　ill…disposed　person；　it　was　the　first　criminal　act　of　that　description。

James　Starr　was　of　opinion　that　the　stone　had　bee　detached　from　the　roof　of　the　gallery；　but　Harry　would　not　admit　of　such　a　simple　explanation。 According　to　him；　the　stone　had　not　fallen；　it　had　been　thrown；　for　otherwise；　without　rebounding；　it　could　never　have　described　a　trajectory　as　it　did。

Harry　saw　in　it　a　direct　attempt　against　himself　and　his　father；　or　even　against　the　engineer。

CHAPTER　VI　SIMON　FORD'S　EXPERIMENT

THE　old　clock　in　the　cottage　struck　one　as　James　Starr　and　his　two　panions　went　out。 A　dim　light　perated　through　the　ventilating　shaft　into　the　glade。 Harry's　lamp　was　not　necessary　here；　but　it　would　very　soon　be　of　use；　for　the　old　overman　was　about　to　conduct　the　engineer　to　the　very　end　of　the　Dochart　pit。

After　following　the　principal　gallery　for　a　distance　of　two　miles；　the　three　explorers……for；　as　will　be　seen；　this　was　a　regular　exploration……　arrived　at　the　entrance　of　a　narrow　tunnel。 It　was　like　a　nave；　the　roof　of　which　rested　on　woodwork；　covered　with　white　moss。　It　followed　very　nearly　the　line　traced　by　the　course　of　the　river　Forth；　fifteen　hundred　feet　above。

〃So　we　are　going　to　the　end　of　the　last　vein？〃　said　James　Starr。

〃Ay！ You　know　the　mine　well　still。〃

〃Well；　Simon；〃　returned　the　engineer；　〃it　will　be　difficult　to　go　further　than　that；　if　I　don't　mistake。〃

〃Ye