VOL. LXXXVI.] PHILOSOPHICAL TRANSACTIONS. 41 



the precincts of a Druidical grove, or dwelling, in Ireland. The same kind of 

 celt is described in Wright's Louthiana, b. 14, p. 7, pi. l ; and also in the 

 Archaeologia, vol. 5, p. 113, by Dr. Lort. It weighed 1 and 4. lb. Except at 

 the edge it was nearly -iths of an inch in thickness. It was of a blackish colour, 

 from oxyde of the metal and dirt on its surface. 



6. Fig. 6, represents the Celt, N° 2. It was found in a field, by ploughing, in 

 Cumberland. The celt in Dr. Lort's collection which most resembles this article is 

 delineated by fig. 11, pi. 8, p. 113, vol. 5, of the Archaeologia. The celt before 

 us differs from that just referred to, in being grooved on both sides to receive a 

 shaft or handle, instead of having a socket. It weighed nearly 4 lb., and was 

 about -f-ths of an inch thick, except at the edge. Its external appearance was like 

 that of the former celt. 



7. Fig. 7, represents the Celt, N° 3. It was much smaller than the 2 former, 

 weighing only about 5 oz., but it resembled in shape, fig. 5. 



In § 2. are described the external, or more obvious properties of these arms and 

 utensils. 



In § 3. the specific gravities of these arms and utensils are stated, being mostly 

 contained between the limits 8.3 and 8.9. 



§ 4. Experiments with fire. — (a) These old instruments melted at a lower 

 temperature than that at which copper, or even some kinds of brass melt. Though 

 I did not (says Dr. P.) succeed in determining precisely the temperature at which 

 each of them fuses ; it may be useful to relate the experiments made with that view. 



(b) lOOgrs. of each of the above 7 ancient metallic instruments, and the same 

 quantity of copper, of pure silver, of allay of copper with 4-th of its weight of 

 tin, of allay of copper with -rVth of its weight of tin, of allay of copper with ^th 

 of its weight of tin, of allay of 3 parts of copper with 1 of zinc, and of gun 

 metal, were exposed each in separate coppels, under a muffle, to the greatest de- 

 gree of fire I could produce in the best assay furnace. A pyrometer clay piece of 

 Wedgwood's instrument was also put into each coppel. During 40 minutes ex- 

 posure to fire, not one of the metals melted, except the pure silver*, and the allay 

 with zinc: nor did any of them emit visible vapour, or inflame, except the allay 

 with zinc; nor did any matter ooze out of any of the metals. 



On cooling, it was found that the figure of the metals which had not been 

 melted in the coppels was not altered, but they were changed, either totally or ex«- 

 ternally, into scoria-like black matter. The copper allayed with zinc was found to 

 contain a nucleus of copper within a large proportion of black scoria and white 

 oxyde of zinc. The celt metals were changed into scoriae, including copper-like 



* In Wedgwood's scale it is stated,, that pure silver melts at 28°, and Swedish copper at 27°. But 

 every part of the furnace in the above experiments might not be of the same temperature for the same 

 space of time : and perhaps the state of cohesion and figure of the metal exposed to fire may account 

 for the difference in the degree noted by the pyrometer in my experiment, from that stated in the scale. 

 For I am assured, by Mr. Thos. Wedgwood, that the degree of contraction is uniform among a number 

 of pyrometer pieces, exposed in the same part of the furnace at the same time. — -Orig. 



VOL. xvm. G 



