46 Scientific Proceedings, Royal Dublin Society. 



I went through with these experiments, and obtained results 

 revealing sensibly the loss of buoyant material. 



Thanks to the translueency of the paraffin we are able to 

 examine minutely the appearance and condition of the mineral 

 when imbedded. I have here under the microscope the pellets 

 made up for these experiments. If you will examine with this 

 1" objective the appearance presented by the gold of experiment 

 7, of the cuprite of experiment 10, you will obtain some notion of 

 the efficacy of the melted paraffin to penetrate and surround loose 

 and dendritic bodies. The fragment of cuprite is about twice the 

 size of a pin's head ; it is a maze of little exquisite octahedrons, 

 deep blood-red in colour, and with fine translueency. Around it 

 the disk of paraffin is uniformly translucent ; through it the paraffin 

 has permeated completely, not a crack or bubble visible. Similarly, 

 the gold seems not less perfectly embalmed beneath its silvery 

 veil — free from any visible blemish to mar the accuracy with which 

 we measure its volume. 



Of experiments 4 and 5 it is interesting, perhaps, to note that 

 4 was undertaken with the notion that the mineral being dealt 

 with was barite. Its weight, as a hand specimen, was deceptive, 

 it being penetrated by sphalerite. On getting the result (2*78) it 

 was concluded that an oversight had been made somewhere in the 

 measurements, and experiment 5 was undertaken; this giving 2*77, 

 the specimen was appealed to. Tests then showed it to be calcite. 



I have thought well to include in the Table some of the quanti- 

 ties obtained in working the formula, as bearing on the scale on 

 which the experiments have been made. It is evident that the 

 method can be applied on a much smaller scale still. 



