io astronomic Instruments ; ^c. 243 



Small we suppose the hole at the centre of the plate to be, 

 we should always be troubled to ascertain with certaintv 

 whether the star occupied the centre precisely ; and how- 

 ever little the eve might be moved, the star would appear 

 also to change its jdace; which could not but diminish the 

 accuracy of the operation. But there was a much greater 

 inconv;;nience : it became very difficult to find the star ; 

 and frequently the instant of time in which the observation 

 was to have been made was passed before it could be found 

 in the telescope. Morin remedied it in the following 

 manner : — 



He had put on the object-end of his telescope*, a sight 

 cut in the middle with a slit sufliciently wide answering to 

 the diameter of the field of the telescope: when he wished 

 to observe a star, he placed it above this slit, and conducted 

 it just over the tube; he was certain then of finding it in 

 the telescope, and of being able to place it in the middle ot 

 the small hole of ihc plate. 



Such was the method which Morin pursued in his re- 

 searches : it therefore follov>^ Uiat ht is the first who adapts 

 ed telescopes to instruments mstead.of sighls : but that the 

 kind of eye-hole with which he coyeicti the eye-glass wai 

 neither so convenient nor so exact as the cross wires put iu 

 ihe common focus of the two glasses by M. Auzout about 

 the year i 667; and Morin did not doubt that his inven- 

 tion would afterwards be improved. Let us hear him do 

 justice to himself in this respect. 



He savst, " I do not doubt but they may add to what 

 I have invented some ingenious means which will render 

 its use more exact and more easy. I even desire it very 

 sincerely ; and am ready to give those wl;io shall effect it 

 the just praises which they will merit; contenting mvself 

 with having opened to minds more sulule than mine, roads 

 ■which were hitherto unexplored." An author who speaks 

 •with so nmch modesty of his own work deserves to be fa- 

 vourably heard. 



, I have not been able to determiuc the precise date of this 

 invention of Morin ; but there is great, probability that it 

 preceded a little the cclcbraied discassion of the 30th of 

 March 1634. I shall be more precise as to the lime when 

 they began to observe tlie stars -d\u\ planets in the day-time 

 Vy means of telescopes. iMorin has preserved its history : 

 and this part of his book is written with a lightness and a 



• Scicn. Loiigit, par* i. p. '"'.'>. f Ibid, pars i. p. 5C. 



O 3 pncllij 



