the twentieth day of September at eight
o'clock in the evening
`` The fact that Ker Karraje may be in the position to use Roch 's fulgurator for the defence of the island must also be taken into consideration . Let it be well borne in mind that if its destructive power surpasses anything ever conceived or dreamed of , it extends over a zone not exceeding a mile in extent . The distance of this dangerous zone is variable , but once the engines have been set , the modification of the distance occupies some time , and a warship that succeeds in passing the zone has nothing further to fear . `` This document is written on the twentieth day of September at eight o'clock in the evening and is signed with my name `` THOMAS HART , Engineer . '' The above is the text of the statement I have just drawn up . It says all that is necessary about the island , whose exact situation is marked on all modern charts and maps , and points out the expediency of acting without delay , and what to do in case Ker Karraje is in the position to employ Roch 's fulgurator . I add a plan of the cavern showing its internal configuration , the situation of the lagoon , the lay of the Beehive , Ker Karraje 's habitation , my cell , and Thomas Roch 's laboratory .