Notes on Barometer Construction. 43 



the work resides, as I shall show, in the material nevertheless. 

 If we carefully warm it over a spirit lamp we can bend it 

 into curves corresponding with those of the crooked tube 

 through which it is to pass, and when each of these bends 

 has cooled we find that the whalebone rod has acquired a 

 permanent set. We thus model an instrument whose axis is 

 coincident with that of the crooked tube, and the elasticity 

 and pliability of the rod remains. It gives and recovers itself 

 as we humour it through the channels, and when we have 

 put it in position it is free to be moved to a limited but 

 mostly sufficient extent, so as to exercise the desired friction 

 at the proper place, detaching a minute insect or a speck 

 of dirt or mould, as the case may be. Doubtless this bend- 

 ing property of whalebone may be utilised in the hands of 

 the physicist and chemist in other ways. Of course wood 

 may be bent by heating or steaming, as instanced in boat- 

 building, and in the familiar instance of walking-stick 

 handles ; but in. the case of whalebone we have at the same 

 time the permanent set and the elasticity of the material — 

 a very valuable combination. 



Concerning the use of cane rods for cleaning the interior 

 of glass tubes, a suggestion may also be made. The elasti- 

 city of the Ligneous material and its even cylindrical form 

 recommend the cane for this purpose, but its siliceous glaze 

 is obviously a dangerous element ; this glaze can be readily 

 removed by scraping with a knife, and cane rods thus 

 stripped will be found sufficiently elastic, strong, clean, and 

 safe for purposes of the nature considered. 



For converting the tube open at both ends into the closed, 

 and when required into the bent and shaped barometer 

 tube, the enameller's blow pipe is used. I shaU not enter 

 into details on this point of the construction, as it is a 

 matter of personal education and skill, and general directions 

 of more or less value are to be found in technical works ; 

 but it will suit the limits of this sketch if the essential 

 requirements of this class of operations are concisely stated. 

 In closing, joining, or bending glass tubes they must be 

 gradually heated to the required temperatures ; the thicker 

 the substance of the glass, or the less perfectly it is annealed, 

 the more care will be required in gradually and equably 

 raising its temperature. In closing the ends of tubes a little 

 blowing for producing a hemispherical termination is mostly 

 necessary. Remember that if this be done with the lungs the 



