The idea that a supposed fulfillment of Lich's prediction in August 1840 gave significant momentum to the Second Advent movement is quite disconnected from the reality of those times. The month of August of that year came and then passed and ... it was silence in the Adventist publications. Because there was no internet in those days! The news ware not coming from one corner of the world to the other with the rapidity we are used to in our days. I'll have to get to the file where I wrote down my findings about this but, from the top of my head, it was only by the beginning of the following year that Himmes commented on some reports of events from Turkey which he interpreted as fulfillment of Litch's interpretation.  

Litchs Prediction: Historical Sources, Outcome, Lessons for Today

Litch used Gibbons dates to calculate what he believed at that time to be the fulfillment of the fifth and sixth trumpet. In his pamphlet entitled The Probability of the Second Coming of Christ About A.D. 1843, published in 1838, he writes:

It was given them after the rise of the Ottoman empire, to torment or harass and weaken men (the Roman empire in the east) five months. If these are prophetic months as is probable, it would be one hundred and fifty years. But when did that empire rise? Mr. Miller has fixed on A. D. 1298. Others, among whom is Gibbon, in his Decline and Fall of the Roman Empire, 1299. He says-Othman first invaded the territory of Nicomedia on the 27th of July, 1299. He also remarks on the singular accuracy of the date, a circumstance not often found in the history of those times. He says-"The singular accuracy with which this even, is given, seems to indicate some foresight of the rapid growth of the monster." {1838 JoL, PSC 153.1}

_[..._] Gibbon, an infidel, is so struck with the singular accuracy of the record of the origin of this empire, that he attributes it to some foresight in the historian, of the rapid growth of the monster. But would it not become Christians better, to attribute it to the superintending providence of that Being who had set a bound for that and other empires, which they may not pass? who had given them power to harass and torment the empire of Constantinople five months; and to kill or subject it to their own sway, an hour, a day, a mouth, and a year; the whole being five hundred and forty-one years and fifteen days. {1838 JoL, PSC 154.2}

Thus, placing a great trust on the accuracy of the information provided by Gibbon, Litch ventures to calculate when the second who of Revelation 9 will come to an end. In this pamphlet he declared that it will end in A. D. 1840, some time in the month of August {1838 JoL, PSC 157.1}. As the expected event was nearing, Litchs ardor to tell others about the soon coming of Christ increased. On the 10^th of May 1840, he writes:

I believe the glorious appearing of the Savior will be between the fall of the Ottoman empire, which will probably take place this year, and the termination of 1843; and that by the end of that year all the scenes of judgment and trouble will be passed, and, in the expressive language of inspiration, "the sanctuary will be cleansed." But at what point of time between those periods Christ will make his appearance, whether in 1841-2, or 3, I know not. The signs of the times, as foretold in the Bible, will indicate His near approach, but for the precise time we are commanded to watch. {1841 JoL, APEC 12.1}

August 1840, the time when the expected fall of the Ottoman power was supposed to happen passed away and, for five months there was silence on the subject from Litch and his co-laborers. Then, after the year 1840 itself became history, Himmes comes up with some explanation. The reason for doing that becomes apparent as we read the introductory part of his article:

We have had numerous questions propounded relative to the fall of the Ottoman power within the three last months, both by the friends and opponents of our cause. As we wish to give a full and distinct answer to them all, we present the following article for the satisfaction of that class of our readers. They will not only find all their questions answered, but we hope their faith in the word of God will be confirmed. {February 1, 1841 JVHe, HST 161.2}

The time and event above named have excited deep interest in the public mind for more than a year past. It is therefore proper that the whole subject should be carefully reviewed, and the exact state of the case presented. {February 1, 1841 JVHe, HST 161.3}

Looks like the public were expecting to hear something! And now Himess goes to the burning question:

Has, then, or has not, THE ORIGINAL CALCULATION IN REFERENCE TO THE 11TH OF AUGUST AND THE OTTOMAN EMPIRE BEEN ACCOMPLISHED? {February 1, 1841 JVHe, HST 161.4}

He continues to give the answer, reasoning that the nature of the fall of the Ottoman Empire should be of the same as the nature of its rise. To get a bit clearer, Litch placed the beginning of the second woe not in 1453, when Constantinople felt into the hands of the Turks, but in 1449, when Deacozes, the new Greek ruler of Constantinople ascended to the throne with the permission of the ottoman Turks. That was interpreted as a submission of the Christian power of Constantinople under the protection of an Islamic power. In this case, the reverse of such an event would mark the end of the second woe. And now, continuing his defense, Himmes picks one event connected with the Second EgyptianOttoman War of those years (183941), claiming that to be the placement of the Islamic power which was ruling from Constantinople, under the protection of the Christian powers of Europe. But, was that really the case?

Lets have a closer look at the historical context of those years! It was a period when the Ottoman Empire was declining and, after Greece gained independence from Constantinople at the beginning of 1830s, in its strive for supremacy, the empire entered into conflict with the state of Egypt, nominally under Ottoman control. Previously their ally in their war against the European powers who were giving their support to the Greeks, the Egyptian army started to wage war against the Ottomans, winning a number of battles, and capturing important territories. Eventually, the Ottoman Empire was on the verge of collapse, as the Egyptians were threatening the capital of Constantinople. At this point, fearing that the fall of the Turkish Empire would create a power vacuum in the region, out of which Russia would take a great advantage, France and the Britain stepped in, putting pressure on the Egyptians, so that they felt forced to call off their invasion. This eventually resulted in a peace treaty, signed in 1833. It lasted until 1839, when the second EgyptianOttoman War erupted. This time the Ottoman Empire had the support of Britain, Russia, Prussia and Austria while Spain and initially France were favourable to the Egyptians.

August 11, 1840 is obscure date, comparing with other more relevant dates of the conflict. It was preceded by the Convention of London, signed on 15 July 1840, where the power of Europe offered to governor of Egypt control over certain territories, under the condition to accept the withdrawal of his forces which were threatening again to ruin the Ottoman Empire. 11^th of August was the day when a small British squadron appeared off Beirut (occupied by Egyptian forces), after the Egyptians failed to fulfill the terms of the London agreement.  However, the European powers moved didnt really move to military action until September 1840, when other ships joined up the ones which already landed in August. In the same month of September France turned its support from the Egyptians to the Turks. Open war broke and finally the Egyptian self-declared monarch renounces his territorial claims in front of the young Sultan, backed up by the forces of the European powers.

What was the declared perception of Himmes  over these events, in connection with what Litch predicted in 1838?

In conclusion: I am entirely satisfied that on the 11th of August, 1840, The Ottoman power according to previous calculation, DEPARTED TO RETURN NO MORE. I can now say with the utmost confidence, "The second woe is past and behold the third woe cometh quickly." "Blessed is he that watcheth and keepeth his garments, lest he walk naked and they see his shame." L. {February 1, 1841 JVHe, HST 162.15}

Well, Himmes may have declared satisfied but the Ottoman power survived the whole XIX century and, even more tragic, this world full of sin survived even longer and still survives! Here is an important lesson for us, those living with the hope to see Jesus return during our lifetime. What kind of Bible students are we? And what are we doing when our interpretations prove to be a failure? Continue to build up sophisticated theories, using fanciful arguments, in order to justify by any means our position?

Instead of declaring himself entirely satisfied after the passing of August 1840, Himmes should have turned back to the Bible together with Litch in order to see what was wrong in their position. I think that God was willing to help them understand that the end of the 2300 days of Daniel 8:14 doesnt coincide with the sounding of the last trump the one following quickly (Rev. 11:14) the second woe.  In fact, He gave Willian Foy a vision in 1842 showing that there are 3 steps to the city of God. This was quite contrary with the understanding of the millerites, that Christ would come very soon, even by the next year. They didnt understand much about the 3rd angels message which was to be preached before Christs coming. Well, in the same vision, William Foy was told that the sixth angel has not yet done sounding. Two years after August 1840! I have reasons to believe that, as Jesus was trying to prepare His disciples for the most important moment of the cross by correcting their view on what was soon to transpire in Jerusalem around 31 AD, Jesus also made an attempt to correct the view of the millerites about the true nature of the event which was to take place around 1843. And He does the same thing for us today: tries to correct our wrong views which we dearly cherish. Oh, how difficult that must be!

How shall we search the Scriptures? Shall we drive our stakes of doctrine one after another, and then try to make all Scripture meet our established opinions? or shall we take our ideas and views to the Scriptures, and measure our theories on every side by the Scriptures of truth? Many who read and even teach the Bible, do not comprehend the precious truth they are teaching or studying.  {CW 36.2} 

Men entertain errors, when the truth is clearly marked out; and if they would but bring their doctrines to the word of God, and not read the word of God in the light of their doctrines, to prove their ideas right, they would not walk in darkness and blindness, or cherish error. Many give the words of Scripture a meaning that suits their own opinions, and they mislead themselves and deceive others by their misinterpretations of God's word.  {CW 36.3} 

As we take up the study of God's word, we should do so with humble hearts. All selfishness, all love of originality, should be laid aside. Long-cherished opinions must not be regarded as infallible. It was the unwillingness of the Jews to give up their long-established traditions that proved their ruin. They were determined not to see any flaw in their own opinions or in their expositions of the Scriptures; but however long men may have entertained certain views, if they are not clearly sustained by the written word, they should be discarded. Those who sincerely desire truth will not be reluctant to lay open their positions for investigation and criticism, and will not be annoyed if their opinions and ideas are crossed. This was the spirit cherished among us forty years ago. . . .  {CW 36.4} 

We have many lessons to learn, and many, many to unlearn. God and heaven alone are infallible. Those who think that they will never have to give up a cherished view, never have occasion to change an opinion, will be disappointed. As long as we hold to our own ideas and opinions with determined persistency, we cannot have the unity for which Christ prayed.  {CW 37.1}