6.  With regard to the practice of drawing, it is not necessary to give any directions, the use of the treatise being only to teach the proper method of imitating the figures which are annexed.  It will be proper to incite the scholars to industry, by showing in other books the use of the art, and informing them how much it assists the apprehension, and relieves the memory; and if they are obliged sometimes to write descriptions of engines, utensils, or any complex pieces of workmanship, they will more fully apprehend the necessity of an expedient which so happily supplies the defects of language, and enables the eye to conceive what cannot be conveyed to the mind any other way.  When they have read this treatise, and practised upon these figures, their theory may be improved by the Jesuit’s Perspective, and their manual operations by other figures which may be easily procured.

7.  Logick, or the art of arranging and connecting ideas, of forming and examining arguments, is universally allowed to be an attainment, in the utmost degree, worthy the ambition of that being whose highest honour is to be endued with reason; but it is doubted whether that ambition has yet been gratified, and whether the powers of ratiocination have been much improved by any systems of art, or methodical institutions.  The logick, which for so many ages kept possession of the schools, has at last been condemned as a mere art of wrangling, of very little use in the pursuit of truth; and later writers have contented themselves with giving an account of the operations of the mind, marking the various stages of her progress, and giving some general rules for the regulation of her conduct.  The method of these writers is here followed; but without a servile adherence to any, and with endeavours to make improvements upon all.  This work, however laborious, has yet been fruitless, if there be truth in an observation very frequently made, that logicians out of the school do not reason better than men unassisted by those lights which their science is supposed to bestow.  It is not to be doubted but that logicians may be sometimes overborne by their passions, or blinded by their prejudices; and that a man may reason ill, as he may act ill, not because he does not know what is right, but because he does not regard it; yet it is no more the fault of his art that it does not direct him, when his attention is withdrawn from it, than it is the defect of his sight that he misses his way, when he shuts his eyes.  Against this cause of errour there is no provision to be made, otherwise than by inculcating the value of truth, and the necessity of conquering the passions.  But logick may, likewise, fail to produce its effects upon common occasions, for want of being frequently and familiarly applied, till its precepts may direct the mind imperceptibly, as the fingers of a musician are regulated by his knowledge of the tune.  This readiness of recollection is only to be procured by frequent impression; and, therefore, it will be proper, when logick has been once learned, the teacher take frequent occasion, in the most easy and familiar conversation, to observe when its rules are preserved, and when they are broken; and that afterwards he read no authors, without exacting of his pupil an account of every remarkable exemplification or breach of the laws of reasoning.