As we could not find pure cobalt for sale in the state of foil or wire suitable for thermo-electric experiments, we resolved to prepare it by electrolysis of chloride of cobalt in the way recommended by Mr G. W. Beardslee of Brooklyn, N.Y. For this ther e is require d pur e chlorid e of cobalt of a certain strength to form the electrolyte, and spongy metallic cobalt to form the positive electrode. By the kindness of Dr Crum Brown these were prepared with very great care in the chemical laboratory by Mr Robinson, to whom we are much indebted. The following note of the method of preparation employed has been supplied by Mr Robinson.