Butl. Feran. Cont. Rem., 114. Ch. Ca., 27. Doran vs. Ross, 1 Ves. jun., 57. Lastly, where the estate devised to the ancestor, is merely an equitable or trust estate, and that to his heirs, or the heirs of his body, carries the legal estate, they will not incorporate into an estate of inheritance in the ancestor; as would have been the case, if both had been of one quality, that is, both legal, or both equitable. Fearn. Cont. Rem., 68. For where the limitations are both legal, the estate-tail arises by legal construction or a rule of law; and when the limitations are both equitable (without other ingredients in the case to control the construction), a similar rule is adopted by equity, to preserve an uniformity in construction. But when both the estates are not legal, the application of a legal construction or operation of a rule of law, which must equally affect both, seems to be excluded, by one of the objects of that construction not being a subject of legal cognizance. So when both are not equitable estates, their combination seems to be out of the reach of an equitable construction, to which one of the estates is not adapted. Idem, 78; Et vid., Lord Say and Sele vs. Jones, 3 Bro. P. C, 113; 8 Vin. Abr., 262; Shapland vs. Smith, 1 Bro. C. C, 75; Silvester vs. Wilson, 2 T. R., 444; Venables vs. Morris, 7 T. R. 342, 438.

"Thus stood the law with respect to the rule in Shelley's case, when the famous case of Perrin vs. Blake arose, before the court of king's bench, in the year 1769; a case which, how much soever it has been regretted as having for a time unsettled the law with regard to this celebrated rule, yet has, in the end, been productive of the most important benefits to the profession, by having given rise to the admired essay, from which the preceding observations have been chiefly extracted. The case was this: - One W. Williams seised in fee of a plantation in Jamaica, devised in the following words: - 'should my wife be enseint with child, at any time hereafter, and it be a female, I give and bequeath unto her the sum of 2000 l. etc.; and, if it be a male, I give and bequeath my estate real and personal equally to be divided between the said infant and my son John Williams, when the said infant shall attain the age of twenty-one. Item, It is my intent and meaning, that none of my children should sell or dispose of my estate for longer time than his life; and to that intent I give, devise, and bequeath all the rest and residue of my estate to my son John Williams and the said infant, for and during the term of their natural lives, the remainder to my brother-in-law, J. G. and his heirs, for and during the lives of my son John Williams and the said infant, the remainder to the heirs of the body of my said sons John Williams and the said infant lawfully begotton, or to be begotten, the remainder to my daughters, etc.' Perrin vs. Blake, 4 Burr., 2579; 1 Bl. Rep., 672; Dougl., 329; 1 Hargr. Law Tracts, 490. No other son was born; and the question was, what estate John Williams took under this will? Had this been the case of an executory trust, says Mr. Fearne, the court of chancery might possibly have construed it an estate for life in J. W., upon the clause expressing the testator's will, that his sons should not convey a greater interest than for their lives. But as it was the limitation of a legal and not a trust estate, the court of chancery itself (in conformity to its own established distinctions explained in the above mentioned cases of Leonard vs. Earl of Sussex, 2 Vera., 526; Glenorchy vs. Bosville, Cas. Temp. Talb., 19; Bagshaw vs. Spencer, 2 Atk., 581; 1 Ves., 149), we may suppose, would have decreed it an estate-tail in J. W. The court of king's bench, however, in the case of Perrin vs. Blake, treated those distinctions as too refined; and adjudged, that J. W. took only an estate for life, under the devise in question. A writ of error was brought upon this judgment in the exchequer chamber; in which the judgment was reversed by the opinion of seven judges against one; so that, upon the whole, eight judges were of opinion that John Williams took an estate-tail; and four, that he took only an estate for life. An appeal was brought to the house of lords from the judgment of reversal in the exchequer chamber; but the parties at length compromised the dispute.

"The subsequent cases of Hayes vs. Foorde, 2 Bl. Rep., 698; Hodgson & Ux. vs. Ambrose, Dougl., 337; 3 Bro. P. C, 416; Jones vs. Morgan, 1 Bro. C. C. 218, 219; Thong vs. Bedford, 1 Bro. C. C, 313, and the recent decisions above cited under their respective heads, have again restored the doctrine respecting this celebrated rule to its former authority. And it is now finally settled, that 'neither an intent manifested by the testator to give only an estate for life, nor the interposition of trustees to preserve contingent remainders, nor mere words of condition, describing the order of succession in which the devisees are to take place, nor the introduction of powers of jointuring, or of liberty to commit waste, are of themselves sufficient to vary the technical sense of the words used. It must plainly appear that the testator did not mean to give such an estate as would pass under the words used, unless controlled by such apparent intent.' Per Lord Alvanley, C. J. Poole vs. Poole, 3 Bos. & P., 620, 627. In order to ascertain the testator's presumable intention, in his use of the words, heirs, etc., we cannot refer the student to a better medium than the principles laid down by Mr. Hargrave, in his masterly observations on the rule in Shelley's case. That profound writer observes, that when it is once settled, that the donor or testator has used words of inheritance according to their legal import; has implied them intentionally to comprise the whole line of heirs to the tenant for life; and has really made him the terminus or ancestor, by reference to whom the succession is to be regulated; then it will appear, that being considered according to those rules of policy from which it originated, it is perfectly immaterial whether the testator meant to avoid the rule or not; and that to apply it, and to declare the words of inheritance to be words of limitation, vesting an inheritance in the tenant for life as the ancestor and terminus to the heirs, is a mere matter of course. That on the other hand, if it be decided, that the testator or donor did not mean by the words of inheritance after the estate for life, to use such words in their full and proper sense; nor to involve the whole line of heirs to the tenant for life, and include the whole of his inheritable blood, and make him the ancestor or terminus for the heirs; but intended to use the word heirs in a limited, restrictive, and un-technical sense, and to point at such individual person, as should be the heir, etc, of the tenant for life at his decease; and to give a distinct estate of freehold to such single heir, and to make his or her estate of freehold the groundwork for a succession of heirs; and constitute him or her the ancestor terminus and stock for the succession to take its course from; in every one of these cases the premises are wanting, upon which only the rule in Shelley's case interposes its authority, and that rule becomes quite extraneous matter. The previous inquiry, therefore, will be, whether, by a remainder to the heirs, either general or special, of a preceding tenant for life, it is the meaning of the instrument to include the whole of his inheritable blood, the whole line of his heirs; or to design only certain individual persons answering to the description of heirs at his death. If the former is the sense, the rule always applies; and, by vesting the remainder in the tenant for life, forces it to operate by limitation, even though the instrument should contradictorily and inconsistently add in express terms, that the remainder shall operate as a contingent one, and enure so as to make the heirs purchasers. If the latter sense is adopted, the rule is as invariably foreign to the case; and the remainder consequently is contingent till the death of the tenant for life, upon which event his heir takes it by purchase. 1 Hargr. Law Tracts, 575, 577. This idea of the rule, which will be ever admired for its simplicity and clearness, has been confirmed by Lord Thurlow, in his determination in the case of Jones vs. Morgan, 1 Bro. C. C. 220, and by Mr. Fearne, in his elaborate Essay on Contingent Remainders."