1852.] TIDE-GAUGE ESTABLISHED. 141 



who supplied, by authority of the Admiralty, a most 

 valuable suite of thermometers and other instruments, 

 and spared no exertion to afford valuable information 

 and suggestions for their management. 



As the decrease of temperature would soon prevent 

 the accurate registry of the tides by our tide-pole on 

 shore, I made some experiments on the true rise and fall 

 of the ship, now firmly frozen into the floe, so as to guide 

 me in selecting her as the index of floatation, or tidal 

 level. To determine this truly, I placed the theodolite 

 so that the level wire should coincide with a zero mark 

 on a batten nailed on the ship's side. This instrument 

 being fixed, the readings at each inch, above or below, 

 being compared with the tide-pole already established 

 near the shore, and found to be nearly identical in fact, 

 those indicated by the ship being more decidedly even 

 I had no further hesitation in adopting her as my in- 

 tended gauge. The modus operand! instantly occurred 

 to me, and I at once determined to make it a plaything 

 or complete piece of machinery. This required a little 

 labour in my cabin, but it was soon constructed, and told 

 its own tale, marking the inches of rise or fall by agi- 

 tating a bell. As it will be better understood by a dia- 

 gram, I must refer my readers to it for explanation. 



All seamen will understand the matter without diffi- 

 culty, but I fear that I may not be so fortunate with 

 civilians. It must however be apparent to all, that by 

 affixing a large as well as heavy weight to a rope, and 

 sinking it to the bottom, the weight, provided the bot- 

 tom be firm or gravelly, would gradually acquire a steady 

 position by agitation. This done (at a) below water, and 



