226 Roijal Academy nf Sciences of Paris. 



much the art of gilding with mercury is injurious to the health, 

 kft a legacy of 3()0() francs in favour of the person who should' 

 discover a process bv means of which mercury might he em- 

 ployed without any danger in gilding. Government having ap- 

 proved of this legacy, the Academv published last vear a pro- 

 gram descriptive of the art, the inconveniences of which are 

 sought to be removed; and poii.ting out those particular opera- 

 tions in which the danger is greatest: but no satisfactory memoir 

 on the subject having been pje'euted, the Academy resolved 

 to propose the subject anew for the vear 1818. It is resiuired 

 that the competitors shall jnit in practice in some workshop in 

 Paris the processes which thev propose ; and that these pro- 

 cesses shall be such, that besides eflecting the principal object 

 in view, they may combine some means of re-collecting the eva- 

 porated mercury. The period of competition is limited to the 

 Ist of January iSlS, and the result will be published the first 

 Monday of March 1M8. 



Two other prizes which the Academy had announced last 

 year remaining also unmerited by any of the memoirs which 

 they have called forth, the Academy resolved to propose them in 

 like manner again for the year 1818. 



Both prizes are gold medals of the value of 3000 francs each. 



The subject of the first prize is, " To determine, 1. The ris^ 

 of the thermometer in mercury comparatively with its rise in air 

 from 20" below zero to 200° centig. 2. The law of cooling in 

 a vaciumi. 3. The lau- of cooling in air, hydrogen gas, and car- 

 bonic acid gas, to different degrees of temperature, and according 

 to different states of rarefaction." 



The sul)ject of the second prize is, " To determine the che- 

 mical changes which fruits undergo duiing and after their ma- 

 turation." 



The Academy also resolved to propose the following subjecl; 

 for another prize in physics, to be adjudged in the public sitting 

 of March 1819: " To detcrniine by accurate experiments the 

 defraction of luminous rays, direct and reflected, when they pass 

 separately or simultaneously near the extremities of one or many 

 bodies of an extent either limited or indefinite, having regard to 

 the intervals of these bodies; as also to the distance of the lu- 

 minous body from which these ravs emanate. 2. To deduce 

 from these exjieriments by mathematical induction the motions 

 of rays in their passage near such bodies." — The prize to be a 

 gpld medal of the value of 3000 francs ; and the period of com- 

 petition limited to tire 1st of August 1818. 



SCIENTIFIC 



