I do not speak of those examples which are joined to the several precepts and rules by way of illustration (for of these I have given plenty in the second part of the work); but I mean actual types and models, by which the entire process of the mind and the whole fabric and order of invention from the beginning to the end, in certain subjects, and those various and remarkable, should be set as it were before the eyes.

For I remember that in the mathematics it is easy to follow the demonstration when you have a machine beside you; whereas without that help all appears involved and more subtle than it really is.

To examples of this kind,--being in fact nothing more than an application of the second part in detail and at large,--the fourth part of the work is devoted.
* * * * * The fifth part is for temporary use only, pending the completion of the rest; like interest payable from time to time until the principal be forthcoming.

For I do not make so blindly for the end of my journey, as to neglect anything useful that may turn up by the way.
And therefore I include in this fifth part such things as I have myself discovered, proved, or added,--not however according to the true rules and methods of interpretation, but by the ordinary use of the understanding in inquiring and discovering.

For besides that I hope my speculations may in virtue of my continual conversancy with nature have a value beyond the pretensions of my wit, they will serve in the meantime for wayside inns in which the mind may rest and refresh itself on its journey to more certain conclusions.
Nevertheless I wish it to be understood in the meantime that they are conclusions by which (as not being discovered and proved by the true form of interpretation) I do not at all mean to bind myself.