3 76 Tli Ays ACTIONS OF THE AMElilCAy lySTlTUTE. 



1860, in 1868 and in 1869, along with the spectroscopic observations 

 simultaneonsly made, have thrown a flood of light upon this difficult 

 subject, and have contributed greatly to the establishment of a trust- 

 worthy theory of the physical condition of the sun. And in connec- 

 tion M-ith this topic, I ought not to omit to state that photography 

 has furnished the best, and I might almost say the only effectual 

 mode yet attempted of investigating the laws which govern the solar 

 spots, as to their appearances and disappearances, as to tbeir periods, 

 and as to their distribution and their varieties, by means of impressions 

 of the sun's disk taken daily for long periods of time, and compared 

 with each other according to a severe mathematical method. 



This is far from being an exhaustive enumeration of the uses of 

 photography. Its scientific applications are far more numerous, and 

 new practical uses for it are presenting themselves every day under 

 the observation of all of us. Yet the catalogue of your exhibition of 

 1839 contains no mention of photography, for in 1839 photography 

 had never been heard of. It was, indeed, in that very year, if my 

 memory serves me, that a statement appeared in the public prints to 

 the effect that some person in Paris had succeeded in pernjanently 

 fixing the fleeting images of the caraera ohscura / but it is probable 

 that this statement was regarded by most readers rather as an experi- 

 ment upon the credulity of the public than as a true record of an 

 accomplished fact. 



Take anotlier example. In your machine gallery there is at pres- 

 ent exhibited, in several forms, a most powerful engine for elevat- 

 ing water, called the centrifugal pump. For simplicity in the mode 

 of applying power, there is nothing in all the machinery of hydraulics 

 to be compared to it. For rapidity of operation, for the compactness 

 of its own bulk as compared with the volume of liquid which it raises 

 in a given time, it is equally without a parallel. This machine has 

 been the means of saving vessels from foundering, when leaking so 

 heavily that all other forms of pump would have been perfecth' useless. 

 In your present exhibition it stands among the objects of most promi- 

 nent interest ; but it was unmentioned in your catalogue for 1839, for in 

 that year tlie centrifugal pump had not been thought of. 



Turn fur another exam})le to the opposite side of this vast area. 

 You see there a printing press^ which, receiving its paper from a con- 

 tinuous roll, without any guidance from huuuin hands, delivers it in 

 finished sheets, ]>rinted on both sides, wnth such rapidity as to keep 

 an attendant fully occupied in removing its completed work. In 



