Larger tunnel boring machines were also tried by the Germans and the British.¹⁰ The Germans investigated the use of an electrical machine following the British mine blows at Hill 60 in April 1915, to overcome the difficulty that they experienced in pushing forward tunnels in the sector. On 4 June a detachment of three officers, 12 NCOs and 96 pioneers of the Experimental Pioneer Company (Pionier=Versuchs=Kompagnie) travelled to Erkelenz in the Rhineland, where they trained for two weeks at the works of the Internationale Bohrgesellschaft. A second detachment followed on 21 June. They were trained to operate a machine which seems to have measured about 1.20 x 3.50m and at the beginning of August the detachment began preparation of a dugout to house the machine on the eastern edge of Hill 60. The intention was to drive a tunnel of about 82m length to blow up the British position in front of the 143rd Infantry Regiment. Preparation of the dugout was long and difficult, as all of the spoil had to be removed in sandbags, presumably for the sake of secrecy. By 9 August it was at a depth of 2.20m and a dugout was also begun for transformers. Both were completed by 14 August. At the same time the high-voltage cable was laid from a farm on the Kortewilde–Zandvoorde road towards Klein Zillebeke. The cables suffered continuous damage from shellfire, and the bringing forward of the pipes, machinery and equipment was ‘infinitely laborious’.¹¹ On 19 August the machine and cable were in place and two transformers were then installed. The machine was ready to begin cutting on 22 August at a depth of 4.20m with a gradient of one in twenty. Progress forward, however, was very slow and the machine had to be halted frequently for long periods in order to remove the build up of mud. Although a British camouflet at 2am on 26th did not delay work, two days later the machine had to be stopped owing, it appears, to unevenness of the soil causing the cutting head to race and become damaged. A second boring, parallel to the first, was begun on 5 September and advanced 56m in four days. The effect of the local conditions, however, meant that it had to be halted for maintenance and to lay new cables underground. Strong artillery fire also caused a halt, although it was unaffected by a powerful British camouflet on 11 September. Another drilling was set up for the 15th, 80cm beneath the first, on a gradient of one in fifty, but after only two days it had to be extracted because of ground water and running sand and a new foundation of reinforced concrete 1.20 x 3.50 by 0.25m was constructed. Heavy artillery meanwhile made transport more difficult and caused casualties. Large portions of the cables were buried and were frequently cut by shells. On 19th a new tunnel was begun and after about two days around 71m was excavated. After 55m power from the low tension cables from the transformers to the machine became very feeble. The power consumption rose metre by metre and this boring also had to be abandoned. Repair work had become necessary. Another British camouflet in the path of the tunnel did not affect the work, but it seems to have been accepted that the machine was not a success and on 2 October the company was ordered to the sector of the 39th Division to take over mine workings on either side of the Menin Road. The machine was taken from Hill 60 back to Hollebeke and the bringing back of the power cables was only completed on 28 October. The machine seems not to have been tried again.

The British tried two tunnelling machines with no more success than the Germans. The first, tried at Petit Bois in a second shaft sunk at Van Damme Farm, operated at a far greater depth than the German machine, through the clay at 100ft depth. The compressed air-driven Stanley Heading Machine was lowered in parts down the shaft and first tried on 4 March 1916. It cut a 5ft diameter tunnel, moving forward at 2ft per hour. The machine, however, had a tendency to dive and each time it was stopped the newly exposed clay swelled and gripped it tightly, requiring it to be dug out by hand. The power output was insufficient and the fuses of the generator powering the compressor repeatedly blew. After 200ft had been managed Harvey ordered it to be abandoned in the tunnel.¹² A second British machine, a Whittaker, was installed exactly a year later by the 1st Canadian Tunnelling Company at a similar depth, from a shaft in the embankment of the Ypres Canal opposite the Bluff, to carry out a 4,320ft projected drive towards the Dam Strasse. This machine was no more successful than the first at coping with difficult ground and was subsequently dismantled and removed.¹³

Military mining before 1914 was not practised at any great depth and did not anticipate detailed geological knowledge. Traditionally, the object in siege works was to drive tunnels which were as shallow as possible, and knowledge of the underlying strata was rarely needed. For the first time, tunnels were being driven at depths which would pass through several different layers and the location in Flanders of the Paniselien and Ypresian clay levels was crucial to the British Messines plan. Such geological knowledge was also required for constructing deep dugouts and detailed maps were drawn up by both sides to indicate where in Flanders their construction was feasible. Geological knowledge was also vital for the fundamental requirement of water supply. The British Army did not have geologists on its staff, which necessitated the co-opting of civilian experts. Once again the Territorial Force provided the bridge by which expertise was brought into the BEF, when Lieutenant W.B.R. King, formerly of the British Geological Survey and serving in the Royal Welch Fusiliers, was attached to the Engineer in Chief at GHQ from June 1915. The head start that the British had in reaching the clay levels at Messines was due in large part to shortcomings in geological knowledge in the German Army. A German geological investigation of the Messines–Wytschaete ridge prior to the British success in March 1916 would, in the view of one German military geologist, have enabled the Germans to take countermeasures in time to stop the British mining offensive.¹⁴ Serving as a temporary Major with the Australian Mining Corps was an eminent Professor of Geology from Sydney University, T.W. Edgeworth David. David made many important contributions to the geological knowledge of the British sectors of the Western Front. In particular he established the seasonal fluctuation of water levels in the chalk areas, which prevented the British systems being driven below the level at which they would be flooded by the rise in early spring.¹⁵