2o8 Whether Telefcopes were known to the Ancients, 



was fortified by a paffage of Ditmar, bifhop of Merfbourgh, who, at ^he end of his fixA 

 book, fpealcing of Gerbert, afterwards pope Silvefter II. cxpreflbd himfelf thus : « He pef- 

 fc<SHy knew the courfe of the ftars, and exceeded his cotemporaries in the variety of hiS' 

 knowledge. When driven from his own country, Ik: repaired to the emperor Otho, at 

 whofe court he remained a long time. He conftrudted a clock at Magdebourgh, and to af- 

 certain its accuracy, he obferved with a tube theftar which direds mariners *." It is thought 

 that Ditmar, by the word tube, meant the aftronomical telefcope, which, in fafl, has a tube. 

 Strabo alfo mentions a tube of this kind, if we admit that the text is not in this place cor- 

 rupted. " 1 he difc of the fun acquires a more confiderable apparent magnitude at the rifing 

 and fetring of that luminary out al iea, on account of the quantity of vapours which rife 

 from the water, and becaufe the fight, refrafled through thefe vapours, in the fame manner as. 

 through tubes f, receives the images of a larger fize." 



Thefe paffages appear to me to be the ftrongcft which have been brought in proof that 

 tclefcopes were known to the ancients. But it is very furprizing that this knowledge, if it 

 exifted, could have been loft to fuch a degree, that before the feventeenth century the moft 

 fkilful and learned aftronomers fliould not even fufpe£t its exiftence. Men have, at all times, 

 applied to ftudy the courfe and pofition of the fiars. No one is ignorant with what ardour 

 the Greeks, the Arabs, and the Latins, cultivated aftronomy, and how much this fiudy, 

 encouraged by the liberality of princes, has been conftantly purfueJ.. Can it be fuppofed that 

 the ancient obfervers defpifed an inftrument fo ufeful to their labours ? I admit that much of 

 the knowledge of antiquity has been loft by wars, by ravages, and a multiplicity of other 

 caufes ; but if this fubjedt be attentively examined, it will be feen tliat the information 

 which has been loft, relates either to ob}e6ls of luxury, or is of fuch a nature, that greater 

 fubfequent difcoveries muft have caufed them to be neglefted ; and ftill they are not fo loft 

 but that fome trace of their ancient exiftence remains. But this is not the cafe with tclef- 

 copes ; for we have no defcription in the writings of the ancients which can agree with them. 

 Strabo fpeaks of tubes uvXmv; but nothing leads us to apprehend that they, were ufed to 

 obferve the magnitude and courfe of the ftars ; for I cannot fay that I place much depend- 

 ancc on the conjedture of Theodore Almeloven, who thinks that Strabo wrote iJaAwv 

 (glafles). In faft, cryftal, or glafs, is particularly endued with the property mentioned in this 

 paflage of the geographer. But let us fuppofe that Strabo wrote ocvXmv. (tubes), who fliall 

 affure us that thefe tubjs were provided with glalTes ? The fame queftion may be offered 

 refpefting the painting of the monk Conrad. In faft, though it reprefents an inftrument 

 confiderably refembling a telefcope, who can prove that this inftrument contained glaftes like. 

 our telefcopes, which without them would be of little utility? I am almoft certain that 

 tube of Gerbert, of which Ditmar fpeaks, had them not; and in order that Imay not be 

 accafed of deciding eafily, I offer the following proof. Father Mabillon, in his Analeda, has 



* CoDfiderata per fillulam quadam ftelia nautarum ducci. 

 \. iia- II a-j}.ii1. Lib. 3. p. 138. 



publiflied 



