Fufton of Ice by Water repofiiig upott it. 563 



nous of all the colours, afFeiSling the fenfes mod ftrongly *." Now, befides that this is 

 an aflertion oppofed by the pofitive experiment juft now quoted, I think an anfwer may be 

 thus made to it : The white light, from which the fpeclrum is never free, which inclines to 

 yellow, and which is compofed alfo of red, abounds in the yellow and orange of the fpec- 

 trum; fo that both of thefe colours derive their fuperior lullre rather than in tenfity from 

 this circumftance ; or, if they have any degree of the latter more than the red, it is in fad 

 owing to their mixture with the red and the other rays which are all in the white. 

 [To be continued.^ 



IX. 



^tt Account of the Manner in which Heat is propagated in Fluids, and its general Confequinces 

 in the Economy of the Univerfe. By BENJAMIN Count of RUMFORD, 



[Concluded from p. 348.] 



AN order to afcertain the ai£lion of water upon ice retained beneath it, Count Rumford 

 took a cylindrical glafs jar, 4,7 inches in diameter, and 13,8 inches high. Into this he put 

 43,^7 cubic inches, or i lb. i li oz. troy of water. When the jar had been placed in a 

 freezing mixture, and the water was congealed, the ice adhered firmly to the bottom and 

 fides of the jar, and was juft three inches high. The jar was then placed in a mixture of 

 pounded ice and pure water, and kept in that fituation for four hours, in order that the cake 

 of ice might be brought to the temperatnre of 32 degrees. 



The jar (till Handing in a (hallow difli in the pounded ice and water, the furfaceof which 

 cold mixture was juft on a level with the furface of the ice in the jar, 73- oz. trov of 

 boiling hot water were gently poured in, which filled it to the height of eight inches above 

 the furface of the jar. 



In thefe experiments it was evidently of the greateft confequence to prevent thofe irre- 

 gularities which would arife from the a£lion of pouring. The expedient firft adopted for 

 this purpofe was to cover the ice with a circular piece of ftrong pjper, which was gently 

 removed after the pouring. But this not being thought fufficiently effedlual, a flat fliallow 

 dlfh of light wood, half an inch deep, and fomewhat lefs externally than the diameter of 

 the jar, was provided. Its bottom was about a quarter of an inch thick, and was perforated 

 with a great number of fmall holes, which gave it the appearance of a fievc. This per- 

 forated wooden difh, having been previoudy made ice-cold, was placed on the furface of the 

 ice in the jar, and the hot water was gently poured into the difli through a long wooden 

 tube. As the perforated difli floated and remained conftantly at the furface of the water, 

 and as the water pafling through many hundreds of fmall holes was not projefled down- 

 wards with force, the violent motions in the mafs of water in the jar were thus in a great 

 jneafure prevented. The water was not fuffered to idue from the wooden tube in a per- 

 pendicular ftream ; but, the bore being clofed, it was made to ifluc horizontally through a 

 lumber of fmall holes in the fides of the tube at its lower end. 



• Optics, Book i. Part I. Prop. 7, 



4C2 As 



