ect on science could not be long delayed。 Quite independently of the Byzantine influence； however； the striving for better intellectual things had manifested itself in many ways before the close of the thirteenth century。 An illustration of this is found in the almost simultaneous development of centres of teaching； which developed into the universities of Italy； France； England； and； a little later； of Germany。 The regular list of studies that came to be adopted everywhere comprised seven nominal branches； divided into two groupsthe so…called quadrivium； comprising music； arithmetic； geometry； and astronomy； and the trivium comprising grammar； rhetoric； and logic。 The vagueness of implication of some of these branches gave opportunity to the teacher for the promulgation of almost any knowledge of which he might be possessed； but there can be no doubt that； in general； science had but meagre share in the curriculum。 In so far as it was given representation； its chief field must have been Ptolemaic astronomy。 The utter lack of scientific thought and scientific method is illustrated most vividly in the works of the greatest men of that periodsuch men as Albertus Magnus； Thomas Aquinas； Bonaventura； and the hosts of other scholastics of lesser rank。 Yet the mental awakening implied in their efforts was sure to extend to other fields； and in point of fact there was at least one contemporary of these great scholastics whose mind was intended towards scientific subjects； and who produced writings strangely at variance in tone and in content with the others。 This anachronistic thinker was the English monk； Roger Bacon。
ROGER BACON Bacon was born in 1214 and died in 1292。 By some it is held that he was not appreciated in his own time because he was really a modern scientist living in an age two centuries before modern science or methods of modern scientific thinking were known。 Such an estimate； however； is a manifest exaggeration of the facts； although there is probably a grain of truth in it withal。 His learning certainly brought him into contact with the great thinkers of the time； and his writings caused him to be imprisoned by his fellow…churchmen at different times； from which circumstances we may gather that he was advanced thinker； even if not a modern scientist。 Although Bacon was at various times in durance； or under surveillance； and forbidden to write； he was nevertheless a marvellously prolific writer； as is shown by the numerous books and unpublished manuscripts of his still extant。 His master…production was the Opus Majus。 In Part IV。 of this work he attempts to show that all sciences rest ultimately on mathematics； but Part V。； which treats of perspective； is of particular interest to modern scientists； because in this he discusses reflection and refraction； and the properties of mirrors and lenses。 In this part； also； it is evident that he is making use of such Arabian writers as Alkindi and Alhazen； and this is of especial interest； since it has been used by his detractors； who accuse him of lack of originality； to prove that his seeming inventions and discoveries were in reality adaptations of the Arab scientists。 It is difficult to determine just how fully such criticisms are justified。 It is certain； however； that in this part he describes the anatomy of the eye with great accuracy； and discusses mirrors and lenses。 The magnifying power of the segment of a glass sphere had been noted by Alhazen； who had observed also that the magnification was increased by increasing the size of the segment used。 Bacon took up the discussion of the comparative advantages of segments； and in this discussion seems to show that he understood how to trace the progress of the rays of light through a spherical transparent body； and how to determine the place of the image。 He also described a method of constructing a telescope； but it is by no means clear that he had ever actually constructed such an instrument。 It is also a mooted question as to whether his instructions as to the construction of such an instrument would have enabled any one to construct one。 The vagaries of the names of terms as he uses them allow such latitude in interpretation that modern scientists are not agreed as to the practicability of Bacon's suggestions。 For example； he constantly refers to force under such names as virtus； species； imago； agentis； and a score of other names； and this naturally gives rise to the great differences in the interpretations of his writings； with corresponding differences in estimates of them。 The claim that Bacon originated the use of lenses； in the form of spectacles； cannot be proven。 Smith has determined that as early as the opening years of the fourteenth century such lenses were in use； but this proves nothing as regards Bacon's connection with their invention。 The knowledge of lenses seems to be very ancient； if we may judge from the convex lens of rock crystal found by Layard in his excavations at Nimrud。 There is nothing to show； however； that the ancients ever thought of using them to correct defects of vision。 Neither； apparently； is it feasible to determine whether the idea of such an application originated with Bacon。 Another mechanical discovery about which there has been a great deal of discussion is Bacon's supposed invention of gunpowder。 It appears that in a certain passage of his work he describes the process of making a substance that is； in effect； ordinary gunpowder； but it is more than doubtful whether he understood the properties of the substance he describes。 It is fairly well established； however； that in Bacon's time gunpowder was known to the Arabs； so that it should not be surprising to find references made to it in Bacon's work； since there is reason to believe that he constantly consulted Arabian writings。 The great merit of Bacon's work； however； depends on the principles taught as regards experiment and the observation of nature； rather than on any single invention。 He had the all…important idea of breaking with tradition。 He championed unfettered inquiry in every field of thought。 He had the instinct of a scientific workera rare instinct indeed in that age。 Nor need we doubt that to the best of his opportunities he was himself an original investigator。
LEONARDO DA VINCI The relative infertility of Bacon's thought is shown by the fact that he founded no school and left no trace of discipleship。 The entire century after his death shows no single European name that need claim the attention of the historian of science。 In the latter part of the fifteenth century； however； there is evidence of a renaissance of science no less than of art。 The German Muller became famous under the latinized named of Regio Montanus （1437…1472）； although his actual scientific attainments would appear to have been important only in comparison with the utter ignorance of his contemporaries。 The most distinguished worker of the new era was the famous Italian Leonardo da Vincia man who has been called by Hamerton the most universal genius that ever lived。 Leonardo's position in the history of art is known to every one。 With that； of course； we have no present concern； but it is worth our while to inquire at some length as to the famous painter's accomplishments as a scientist。 From a passage in the works of Leonardo； first brought to light by Venturi；＇1＇ it would seem that the great painter anticipated Copernicus in determining the movement of the earth。 He made mathematical calculations to prove this； and appears to have reached the definite conclusion that the earth does moveor what amounts to the same thing； that the sun does not move。 Muntz is authority for the statement that in one of his writings he declares； 〃Il sole non si mouve〃the sun does not move。＇2＇ Among his inventions is a dynamometer for determining the traction power of machines and animals； and his experiments with steam have led some of his enthusiastic partisans to claim for him priority to Watt in the invention of the steam…engine。 In these experiments； however； Leonardo seems to have advanced little beyond Hero of Alexandria and his steam toy。 Hero's steam…engine did nothing but rotate itself by virtue of escaping jets of steam forced from the bent tubes； while Leonardo's 〃steam…engine〃 〃drove a ball weighing one talent over a distance of six stadia。〃 In a manuscript now in the library of the Institut de France； Da Vinci describes this engine minutely。 The action of this machine was due to the sudden conversion of small quantities of water into steam （〃smoke；〃 as he called it） by coming suddenly in contact with a heated surface in a proper receptacle； the rapidly formed steam acting as a propulsive force after the manner of an explosive。 It is really a steam…gun； rather than a steam…engine； and it is not unlikely that the study of the action of gunpowder may have suggested it to Leonardo。 It is believed that Leonardo is the true discoverer of the camera…obscura； although the Neapolitan philosopher； Giambattista Porta； who was not born until some twenty years after the death of Leonardo； is usually credited with first describing this device。 There is little doubt； however； that Da Vinci understood the principle of this mechanism； for he describes how such a camer