(2022年3月6日 追記) 文献からの引用を追記しました。
Twitterで以下の文章が話題になっていました．ツイートをされた方は「英語勉強法.jp」の野村勇介先生です.
Many a time that first day of my journey did I have cause for thankfulness that had taken the precaution to learn means for determining the points of the compass, for the knowledge saved me many a weary mile.
— 野村勇介 (@YSK_NMR) April 13, 2020
これ難しいですね。
Many a time that first day of my journey did I have cause for thankfulness that had taken the precaution to learn means for determining the points of the compass, for the knowledge saved me many a weary mile.
Marooned in the forest by Alpheus Hyatt Verrill
今回の記事の内容
論点① "Many a time ..."という時・頻度を指す副詞句が文頭に来たため，主語・助動詞の倒置が生じている（随意的）．
論点② thankfulnessの理由を表すthat節内の主語"I"が抜けている．
■論点① 主語・助動詞の倒置について
"Many a time that first day of my journey"という時（頻度）を表す副詞句が文頭にあり，did I have ...と疑問文の語順（助動詞→主語）になっています．
文全体は疑問文ではなく，"Many a time that first day of my journey did I have ..."を条件節（従属節）として取るような主節が他にないことから，平叙文の主節において，副詞句の前置により，主語・助動詞の倒置が生じていると考えられます．
敢えて言えば"Many a time ..."が焦点となるときに生じる倒置と考えられますが，否定語句を文頭に前置したときの倒置（助動詞→主語）などと異なり随意的です．この本には4回 "Many a time"が文頭に出てきますが，他の3回はすべて倒置されていません．参考に一例を引用します．
Many a time when a boy I had speared frogs when spending my summers on a farm, and now that frogs were in my mind I remembered the two- or three-pronged spears which the farmers’ boys used. I was still hungry, and while my frog was broiling I busied myself in making a real frog-spear. It was not a difficult task.
https://www.mstrust.org.uk/news/i-am-not-lazy-merely-fatigued-wills-story
この倒置自体は現代でも見られるものです．以下に引用するのは，多発性硬化症という難病の患者が疲労"fatigue"について語った文章です．
Fatigue doesn't necessarily manifest as tiredness, subjectively. In the same way that a low blood sugar level doesn't always feel like hunger, or dehydration like thirst. Many a time have I thought I was hungry when I was merely bored.
(2022年3月6日 追記)
文献を追記しておきます。
3.3.6 Many / much / more / most
After openers containing these elements we normally find straight order . Inversion is only found in slightly archaic style :
Inversion in Present-day English by Hans H. Hartvigson and Leif Kvistgaard Jakobsen
Many/much/more /mostの後に、主語と(助)動詞の倒置が起こることがありますが、やや古風な表現に限られ、文体的な倒置であるとされています。
上記文献からいくつか例文を引用します。
( 140 ) For many a time did I sit on the banks of the banks of the blue and green lake reflecting how highly these intelligent loafers, whose regard I valued, would regard me MSR 92
(141) Oh many times did Ernest Hyde and I argue about the freedom of the will, MCLUS 262.
(142) More than once had Stella been annoyed by reticences on the part of Martha and Alice ..l DLPM 104
(144) Many a rabbit had he snared, without the gamekeeper noticing it. (q. Zandvort p.239)
(144)では副詞要素ではなくMany a rabbitという目的語が文頭に前置されることで、その後に続く主語と助動詞の倒置が起きています。
Zandvort著A handbook of English Grammarの689にて、目的語が文頭に来る時、主語と(助)動詞の倒置が起こることがあるとして、上記(144)の例文を紹介しています。その条件として、manyやmuchのようなemphaticまたはemotionalな単語に続く目的語が文頭に前置されたばあいに限って、倒置が起こると述べています。
The construction is only found, however, after an object preceded by such an emphatic (and emotional) word as much or many; one would not normally say or write: *.A rabbit had he snared.
A handbook of English Grammar by Zandvort
また、以下のように興味深い記述もあります。
690. As was pointed out in 202, inversion caused by front-position of an adjunct or object occurs chiefly in emphatic or emotional style. In more matter-of-fact communications the adjunct or object either does not have front-position (We often went for walks together; He had snared many a rabbit); or if it has, it does not cause inversion (After some time they saw a light). In the former case there is an alternative (Often did we go . . .); in the latter there is none.
A handbook of English Grammar by R. W. Zandvort
同節では、1つの文の中に、類似した2つの節が異なる語順で表れている例として、Trevelyanの一節が引用されています。
In Ulster alone had the tenant some protection, and in Ulster alone the population was largely British and Protestant. History of England by G. M. Trevelyan
Poutzmaの紹介はやや長くなるので記事末尾に追記します。
■論点② 誤植
なお，"cause for thankfulness that had taken the precautions to learn ..."の部分について，コンパスの扱いを予め身につけておいた主体は"I"ですから，"cause for thankfulness that I had taken the precautions to learn ..."から"I"が抜けた誤植と考えられます．"have reason/cause for thankfulness that ..."は "..."ということに感謝する理由があるという意味です．この場合，that節の役割は，"I am thankful that ..."で感謝の理由を表す副詞節と同様のものと考えられます．
■おまけ
Many a time that first day of my journey did I have cause for thankfulness that I had taken the precaution to learn means for determining the points of the compass, for the knowledge saved me many a weary mile.
私の旅の初日には，念のためあらかじめ方角を確認する方法を学んでおいたことに感謝する機会が何度もあった．というのも，その知識によって何マイルもの疲れる道のりを余計に歩かずに済んだからだ．
for は独立した節をつなぐ理由の等位接続詞．理由といっても因果関係を説明するというより，前に述べたことについて解説するという役割があります．
■まとめ
基本的に英文の内容が分からない場合には，自分の解釈が間違っている可能性を考える方がよいと思います．ただし，今回のように本文が間違っていると考えられる場合もあるので注意しましょう．
◾️おまけ その2 (2022年3月6日追記).
以下は全てPoutsmaのA handbook of Late Modern Englishからの引用です。
まずは副詞要素が前置され、主語と(助)動詞の倒置が生じている例について
8章8節のjとkより
In sentences or clauses opening with an adverbial adjunct or clause, the subject, whether noun or pronoun, is not unfrequently found after the finite verb of a complex predicate; thus in:
We have been very happy here. But if Bell should leave you — " — "Then should I go also." Trol., Small H o u s e, I, Ch. XXVII, 321.
The more carefully it (sc. Addison's character) is examined, the more will it appear sound in the noble parts. Mac, Addison, (733a).
Yet was the spirit of the haughty daughter of the Caesars unbroken, id., Fred., (668 b).
To them will nothing be trivial. Mer., Rich. Fev., Ch. XXV, 189.
In vain have I sung and laboured; in vain I went down to the dead. Kingsley, The Heroes, II, in, 129.
(Observe the varied practice.) Daily are men induced to aid in carrying out inventions which a mere tyro in science could show to be futile. Spenc, E d u c, Ch. I, 22 b.
So had Nanno come to London. Temple Thurston, Traffic, III, Ch. IV, 141
Many a summer evening liave Boy Jim and 1 lain upon the grass, watching all these grand folk. Con. Doyle, R o d n. Stone, I, Ch. 1, 22.
In such surroundings was an extraordinary man born. Arn. Bennett, The Card, Ch. I,1.
k) The word-order in the following examples, presumably common enough in older English, is now only occasionally met with, except, perhaps, in the language of the illiterate.
Mrs. Frail. What have you to do to watch me ! 'slife, I'll do what I please. Mrs. Fore. You will? Mrs. Frail. Yes, marry will 1. Congreve, Love for Love, 11, 2, (231).
"He speaks the truth," said a second voice firmly. "Ay, that doth he," said a third. Lytton, Rienzi, I, Ch. HI, 22.
"Has morning come already?" asked Nicholas, sitting up in bed. — "Ah! that has it," replied .Squeers Dick., Nick., Ch. VIII, 436.
"Then Mr. Rochester was at home when the fire broke out?" — "Yes, indeed, was he." Ch. BrontE, Jane Eyre, Ch. XXXVI, 527.
Certainly three times a week do 1 have to put up with his company .El. Glyn, Ref I. of Am bros., I, Ch. ii, 26.
8章9節(a)より
Inversion is less frequent in sentences opening with an adverbial adjunct or clause in which the verb is accompanied by an object. Nor is it dependent on the relative weight of the subject and the predicate.
Most humbly do I take my leave. Shak., H a m I., I, 3, 83.
With very different impressions did the unfortunate lover regard the tidings. Scott, Fair Maid, Ch. XXXIII, 348.
With inconceivable satisfaction did the new landowner settle himself in his comfortable homestead. Lytton, C a x t., II, Ch. II, 33.
In vain did the enemy himself invest in a pea-shooter Hughes, Tom Brown, I, Ch. Ill, 239.
8章14から、目的語が前置され、その後に助動詞+主語の倒置が生じている用例に関する記述を一部引用します。
a) When the object is not negative, and is not represented by (13) a quotation or a statement, front-position does not now occasion inversion in ordinary language, in the older language it may have been the rule ; but in Late Modern English it appears to be common only in literary language with an intentional archaic tinge (39);
e.g.: Greater love hath no man than this, that a man lay down his life for his friends. Bible. John, XV, 13.
The tongue can no man tame; it is an unruly evil. Bible, James, ill. 8. Ten thousand falsehoods has this gentleman told me. Golds., Vic. Ch. XXXI, (468).
More than three months of precious time had that martyr of a Major given up to his nephew. Thack., P e n d., I, Ch. XVlll, 182.
A pretty paradise did we build for ourselves, id., Sam. T i t m., Ch. IX, 95.
Her grief at her bereavement knew none. Watts Dunton, Aylwin, II, Ch. VI, 84,h. V, 82.
But his grandson he had refused to see until to-morrow. Dick., C h u z.
