Astronomy and Photography at Rome. 375 



PHOTOGRAPHICAL DELINEATION OF NEBULAE. 



One of the first uses made by Galileo of the telescope, on its 

 invention, was the examination of some of the most remarkable 

 nebulas, and the delineation of their then state, as if he had anti- 

 cipated, future changes in their constitution. In his Siderius 

 Nuncius, published in the year 1610, he gave drawings upon a 

 large scale of the Pleiades, of the Belt and Sword of Orion, of the 

 nebula in the head of Orion, and of the cluster of stars known as 

 the Prsesepe or Bee Hive, in the constellation Cancer. In these 

 the ground is black, and the stars white. The positions of the 

 stars are given with considerable precision, but there is no trace 

 of the remarkable extent of lucid nebulous matter, nor of the 

 deep black indenture and distinct outline which gives it some- 

 thing of the appearance of a bat's wing. The idea of perpetua- 

 ting the appearance of this particular nebula of the Sword of Ori- 

 on in his time, was taken up by Huygens, in the year 1656, and 

 he has left what he vouches for a correct representation of it, as 

 seen by him, but unaccountably passes over in silence the draw- 

 ing left by Galileo. In Huygens's drawing and description, the 

 shape of the nebula differs considerably from that which it now 

 has, and the engraving in Sir John F. W. Herschel's Astronomy 

 for the year 1833, is still more at variance with the present real- 

 ity. In these circumstances, a doubt arises how far the apparent 

 discrepancies are owing to actual physical changes in the nebula 

 itself, or if they be owing to the imperfection of the instruments 

 used, or of the vision or powers of accurate delineation possessed 

 by the observers. That it is owing, in some degree, to physical 

 changes is rendered probable, from alterations which have been 

 seen to take place in the last three years. Fortunately, the Ro- 

 man astronomers have hit on a means effectually to prevent fu- 

 ture mistakes of vision or delineation. They have brought the 

 Daguerreotype to bear on the object, and throwing the photograph- 

 ic image of the nebula and its stars on a lithographic stone; have, 

 by an ingenious invention of the Signor Rondoni, which is still 

 kept secret, fixed it there. From that stone they have been able 

 to take impressions on paper, unlimited in number, of singular 

 beauty, and of perfect precision, each star, each filmy nebulous 

 streak faithfully depicting its own position. The scale is large, 

 proportionate to the magnifying and light-collecting powers of 



