236 ANNUAL OF SCIENTIFIC DISCOVERY. 



he was not encouraged at first on account of his political principles, and, 

 secondly, because the clerical party, which were then all powerful, got up a 

 cry of infidelity against him. His secret found no purchasers, and he died in 

 consequence of a complaint which he had contracted in visiting some of 

 the wildest parts of Africa. A short time after his death, the late Abbe 

 Francesco Baldacconi, director of the Museum of Natural History at 

 Sienna, obtained certain results which led to very strong hopes that Se- 

 gato's secret might be rediscovered. Mr. Baldacconi's process consisted 

 in steeping the anatomical specimens for several weeks in a solution of 

 equal parts of corrosive sublimate and sal ammoniac, a mixture uhich by 

 the earlier chemists was called sal alembroth ; and in 1844 a liver thus 

 prepared was sent over by him to the Academy of Sciences in Paris. 

 This specimen had acquired the consistency of steatite, or of serpentine, 

 and was perfectly incorruptible. The Italian papers now state that a 

 Sardinian naturalist, Prof. Marini, has rediscovered Segato's secret. His 

 process is also kept a secret, but from the description it appears that he 

 obtained still more remarkable results th in his predecessor. He has con- 

 structed a small table entirely composed of petrified animal substances, 

 viz: brain, blood, and gall, and having quite the appearance and con- 

 sistency of breccia. His preparations are incorruptible ; they preserve 

 their natural color and will resume their original state on being immersed 

 in water for some time. Silliman's Journal. 



PETTENKOFEIl'S PROCESS OF RESTORING PICTURES. 



During the last year or more, considerable attention has been drawn 

 to a discovery by Dr. Pettenkofer of Munich, Germany, of a method 

 of restoring old paintings to their original beauty and freshness. The 

 method, which has been tried with the most satisfactory results on 

 many valuable pictures, has, however, remained a secret until within 

 the past few months, when the discovery became protected by letters 

 patent, in all the principal countries of Europe. From the specifica- 

 tions of the English patent, we derive the following memoranda. It 

 begins by stating that the process of restoring the surface does not 

 endanger the original state of the oil picture. It proceeds to explain 

 that the unwelcome change which comes over varnished oil paintings 

 after the lapse of years, is, in most cases, owing to physical and not 

 chemical influences. Time causes the discontinuance of molecular co- 

 hesion in particular materials. The change here begins on the surface 

 of the varnish with microscopical fissures, and this system of disinte- 

 gration continues to penetrate even " through the different coats of 

 color to the very foundation." Both the surface and the body of such 

 a picture become intimately mixed with air, and reflect light like pow- 

 dered glass, thus losing transparency like oil mingled Avith water or 

 air. x 



The best method of rejoining the separated particles has been 

 found to be by means of a vapor produced from spirits of wine. Dr. 

 Pettenkoler places the picture, or pictures, in a closed case or bath, 

 the air in which is impregnated with the fumes of alcohol at the ordi- 

 nary temperature and without any application of heat. The resinous 

 particles of the picture thereupon absorb the alcohol until they are 

 saturated, and no longer. By this process the different separated 

 molecules reacquire cohesion with each other, and the optical effect 



