Please note that Mommsen uses the AUC chronology (Ab Urbe Condita), i.e. from the founding of the City of Rome. You can use this reference table to have the B.C. dates
From: The History of Rome, by Theodor Mommsen
Translated with the sanction of the author by William Purdie Dickson
The Senate as State-Council
With this arrangement was probably connected the apparently very ancient usage, in virtue of which the king previously submitted to the senate the proposals that were to be brought before the burgesses, and caused all its members one after another to give their opinion on the subject. As the senate had the right of cancelling the resolution adopted, it was natural for the king to assure himself beforehand that no opposition was to be apprehended from that quarter; as indeed in general, on the one hand, it was in accordance with Roman habits not to decide matters of importance without having taken counsel with other men, and on the other hand the senate was called, in virtue of its very composition, to act as a state-council to the ruler of the community.
It was from this usage of giving counsel, far more than from the prerogatives which we have previously described, that the subsequent extensive powers of the senate were developed; but it was in its origin insignificant and really amounted only to the prerogative of the senators to answer, when they were asked a question. It may have been usual to ask the previous opinion of the senate in affairs of importance which were neither judicial nor military, as, for instance--apart from the proposals to be submitted to the assembly of the people--in the imposition of task-works and taxes, in the summoning of the burgesses to war-service, and in the disposal of the conquered territory; but such a previous consultation, though usual, was not legally necessary.
The king convoked the senate when he pleased, and laid before it his questions; no senator might declare his opinion unasked, still less might the senate meet without being summoned, except in the single case of its meeting on occasion of a vacancy to settle the order of succession in the office of -interrex-. That the king was moreover at liberty to call in and consult other men whom he trusted alongside of, and at the same time with, the senators, is in a high degree probable. The advice, accordingly, was not a command; the king might omit to comply with it, while the senate had no other means for giving practical effect to its views except the already-mentioned right of cassation, which was far from being universally applicable. "I have chosen you, not that ye may be my guides, but that ye may do my bidding:" these words, which a later author puts into the mouth of king Romulus, certainly express with substantial correctness the position of the senate in this respect.
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Reference address : https://www.ellopos.net/elpenor/rome/1-05-original-constitution-rome.asp?pg=32