114 



On the Longitudinal Ewpansioii 



[Jan. 



made on that account, such allowance as the reader may think neceS' 

 sary can be made accordingly. 



13.— The respective rods being conveniently suspended close by the 

 apparatus, and subject to the free air that circulated in the bungalow 

 but shielded from the Aveather, the following table exhibits the results 

 of the first experiment on their lengths t the rods being all unvarnished 

 except No. 6, which was covered with 3 coats of spirit varnish. The 

 mark -j-j plus, signifies that the rod, on being tried, had elongated; the 

 mark — , minus, signifies that it had contracted : tlie figures denote the 

 decimal parts of an inch of the expansion or contraction of each rod 

 respectively. 



00 



1-1 



ci 

 S 



No. I 



jak. 



. s 



o g 



to 

 . a 



o O 

 rt 





d . 



No. 6 

 '"ir. 



Flygro. 







!B 





^ s 





o 



-^^ 















o 



O "rt 



1 



1 PiO 



o J2 



o 



o 



ffl 1 



9 





0.0 



0.0 



0.0 



0.0 



0.0 









10 



Even. 



—0.001 1 



-0.0014 



-0.0030 



-0.0016 



-00019 





73 



82 



11 



Morn. 



0.0 



0.0 



— O.OOll 



0.0 



+ 0.0009 





81 



78 





Even. 



-0.0038 



-0.0042 



-0.0061 



-0.0045 



-0.0073 





66 



82 



12 



Morn. 



+ 0.0003 



■f 0.0006 



0.0 



+0.0008 



+ 0.0027 



+ 0.0013 



82 



78 





Even. 



—0.0012 



-0.0016 



-0.0034 



-0.0016 



— 0.0022 



O.OOll 



73 



83 



13 



Morn. 



4-0.0009 



+ 0.0016 



0.0 



+ 0.0011 



+ 0.0025 



0.0036 



81 



80 





Even. 



—0.0017 



-0.0017 



-0.0036 



— 0.0022 



— 0.0034 



0.0009 



72 



83 



14 



Morn. 



+0.0014 



+0.0014 



- 0.0003 



+0.0014 



+ 0.0025 



0.0040 



81 



81 



26 



Even. 



-0.0019 



-0.0019 



-0.0031 



-0.0022 



-0.0027 



— 0.0003 



7387 



27 



Morn. 



-0.0005 



-0.0003 



-O.OOll 



-0.0006 



+ 0.0008 



+ 0.0011 



79178 



14. — These few experiments made it evident that plain wood, not 

 having been subject to artificial preparation, would lengthen and con- 

 tract so much as to cause a clock with a pendulum made of either of 

 these specimens to keep very uncertain time. "With a view therefore to 

 ascertain whether any advantage would be derived from artificial means, 

 I took the same rods, coated them over with a layer of resin, white 

 candle wax, and linseed oil, having first melted and mixed these sub- 

 stances together over a fire, and with a brush laid the mixture on the 

 rods while it was quite hot. The wood at first absorbed this hot waxy 

 and resinous mixture, but by applying two or three coats, the rods be- 

 came saturated, and when it cooled the wood was thickly coated with it. 

 I then held the rods over a charcoal fire, and broiled the mixture well 

 into them, and when it disappeared, I laid on another coat of it, and 

 rubbed it well into the rods with a cloth. After this, I painted the 

 ^ods over again with the mixture, and again exposed them to the fire. 



