The next day, the 16th of April, and Easter Sunday, the settlers issued from the Chimneys at daybreak, and proceeded to wash their linen. The engineer intended to manufacture soap as soon as he could procure the necessary materials--soda or potash, fat or oil. The important question of renewing their wardrobe would be treated of in the proper time and place. At any rate their clothes would last at least six months longer, for they were strong, and could resist the wear of manual labor. But all would depend on the situation of the island with regard to inhabited land. This would be settled to-day if the weather permitted.
The sun rising above a clear horizon, announced a magnificent day, one of those beautiful autumn days which are like the last farewells of the warm season.
It was now necessary to complete the observations of the evening before by measuring the height of the cliff above the level of the sea.
"Shall you not need an instrument similar to the one which you used yesterday?" said Herbert to the engineer.
"No, my boy," replied the latter, "we are going to proceed differently, but in as precise a way."
Herbert, wishing to learn everything he could, followed the engineer to the beach. Pencroft, Neb, and the reporter remained behind and occupied themselves in different ways.
Cyrus Harding had provided himself with a straight stick, twelve feet long, which he had measured as exactly as possible by comparing it with his own height, which he knew to a hair. Herbert carried a plumb-line which Harding had given him, that is to say, a simple stone fastened to the end of a flexible fiber. Having reached a spot about twenty feet from the edge of the beach, and nearly five hundred feet from the cliff, which rose perpendicularly, Harding thrust the pole two feet into the sand, and wedging it up carefully, he managed, by means of the plumb-line, to erect it perpendicularly with the plane of the horizon.
That done, he retired the necessary distance, when, lying on the sand, his eye glanced at the same time at the top of the pole and the crest of the cliff. He carefully marked the place with a little stick.
Then addressing Herbert--"Do you know the first principles of geometry?" he asked.
"Slightly, captain," replied Herbert, who did not wish to put himself forward.
"You remember what are the properties of two similar triangles?"
"Yes," replied Herbert; "their homologous sides are proportional."
"Well, my boy, I have just constructed two similar right-angled triangles; the first, the smallest, has for its sides the perpendicular pole, the distance which separates the little stick from the foot of the pole and my visual ray for hypothenuse; the second has for its sides the perpendicular cliff, the height of which we wish to measure, the distance which separates the little stick from the bottom of the cliff, and my visual ray also forms its hypothenuse, which proves to be prolongation of that of the first triangle."
"Ah, captain, I understand!" cried Herbert. "As the distance from the stick to the pole is to the distance from the stick to the base of the cliff, so is the height of the pole to the height of the cliff."
"Just so, Herbert," replied the engineer; "and when we have measured the two first distances, knowing the height of the pole, we shall only have a sum in proportion to do, which will give us the height of the cliff, and will save us the trouble of measuring it directly."
The two horizontal distances were found out by means of the pole, whose length above the sand was exactly ten feet.
The first distance was fifteen feet between the stick and the place where the pole was thrust into the sand.
The second distance between the stick and the bottom of the cliff was five hundred feet.
These measurements finished, Cyrus Harding and the lad returned to the Chimneys.
The engineer then took a flat stone which he had brought back from one of his previous excursions, a sort of slate, on which it was easy to trace figures with a sharp shell. He then proved the following proportions:--
15:500::10:x
500 x 10 = 5000
5000 / 15 = 333.3
From which it was proved that the granite cliff measured 333 feet in height.
Cyrus Harding then took the instrument which he had made the evening before, the space between its two legs giving the angular distance between the star Alpha and the horizon. He measured, very exactly, the opening of this angle on a circumference which he divided into 360 equal parts. Now, this angle by adding to it the twenty-seven degrees which separated Alpha from the antarctic pole, and by reducing to the level of the sea the height of the cliff on which the observation had been made, was found to be fifty- three degrees. These fifty-three degrees being subtracted from ninety degrees--the distance from the pole to the equator--there remained thirty- seven degrees. Cyrus Harding concluded, therefore, that Lincoln Island was situated on the thirty-seventh degree of the southern latitude, or taking into consideration through the imperfection of the performance, an error of five degrees, that it must be situated between the thirty-fifth and the fortieth parallel.
There was only the longitude to be obtained, and the position of the island would be determined, The engineer hoped to attempt this the same day, at twelve o'clock, at which moment the sun would pass the meridian.
It was decided that Sunday should be spent in a walk, or rather an exploring expedition, to that side of the island between the north of the lake and Shark Gulf, and if there was time they would push their discoveries to the northern side of Cape South Mandible. They would breakfast on the downs, and not return till evening.
At half-past eight the little band was following the edge of the channel. On the other side, on Safety Islet, numerous birds were gravely strutting. They were divers, easily recognized by their cry, which much resembles the braying of a donkey. Pencroft only considered them in an eatable point of view, and learnt with some satisfaction that their flesh, though blackish, is not bad food.
Great amphibious creatures could also be seen crawling on the sand; seals, doubtless, who appeared to have chosen the islet for a place of refuge. It was impossible to think of those animals in an alimentary point of view, for their oily flesh is detestable; however, Cyrus Harding observed them attentively, and without making known his idea, he announced to his companions that very soon they would pay a visit to the islet. The beach was strewn with innumerable shells, some of which would have rejoiced the heart of a conchologist; there were, among others, the phasianella, the terebratual, etc. But what would be of more use, was the discovery, by Neb, at low tide, of a large oysterbed among the rocks, nearly five miles from the Chimneys.
"Neb will not have lost his day," cried Pencroft, looking at the spacious oyster-bed.
"It is really a fortunate discovery," said the reporter, "and as it is said that each oyster produces yearly from fifty to sixty thousand eggs, we shall have an inexhaustible supply there."
"Only I believe that the oyster is not very nourishing," said Herbert.
"No," replied Harding. "The oyster contains very little nitrogen, and if a man lived exclusively on them, he would have to eat not less than fifteen to sixteen dozen a day."
"Capital!" replied Pencroft. "We might swallow dozens and dozens without exhausting the bed. Shall we take some for breakfast?"
And without waiting for a reply to this proposal, knowing that it would be approved of, the sailor and Neb detached a quantity of the molluscs. They put them in a sort of net of hibiscus fiber, which Neb had manufactured, and which already contained food; they then continued to climb the coast between the downs and the sea.
From time to time Harding consulted his watch, so as to be prepared in time for the solar observation, which had to be made exactly at midday.
All that part of the island was very barren as far as the point which closed Union Bay, and which had received the name of Cape South Mandible. Nothing could be seen there but sand and shells, mingled with debris of lava. A few sea-birds frequented this desolate coast, gulls, great albatrosses, as well as wild duck, for which Pencroft had a great fancy. He tried to knock some over with an arrow, but without result, for they seldom perched, and he could not hit them on the wing.
This led the sailor to repeat to the engineer,--
"You see, captain, so long as we have not one or two fowling-pieces, we shall never get anything!"
"Doubtless, Pencroft," replied the reporter, "but it depends on you. Procure us some iron for the barrels, steel for the hammers, saltpeter. coal and sulphur for powder, mercury and nitric acid for the fulminate, and lead for the shot, and the captain will make us first-rate guns."
"Oh!" replied the engineer, "we might, no doubt, find all these substances on the island, but a gun is a delicate instrument, and needs very particular tools. However, we shall see later!"
"Why," cried Pencroft, "were we obliged to throw overboard all the weapons we had with us in the car, all our implements, even our pocket- knives?"
"But if we had not thrown them away, Pencroft, the balloon would have thrown us to the bottom of the sea!" said Herbert.
"What you say is true, my boy," replied the sailor.
Then passing to another idea,--"Think," said he, "how astounded Jonathan Forster and his companions must have been when, next morning, they found the place empty, and the machine flown away!"
"I am utterly indifferent about knowing what they may have thought," said the reporter.
"It was all my idea, that!" said Pencroft, with a satisfied air.
"A splendid idea, Pencroft!" replied Gideon Spilett, laughing, "and which has placed us where we are."
"I would rather be here than in the hands of the Southerners," cried the sailor, "especially since the captain has been kind enough to come and join us again."
"So would I, truly!" replied the reporter. "Besides, what do we want? Nothing."
"If that is not--everything!" replied Pencroft, laughing and shrugging his shoulders. "But, some day or other, we shall find means of going away!"
"Sooner, perhaps, than you imagine, my friends," remarked the engineer, "if Lincoln Island is but a medium distance from an inhabited island, or from a continent. We shall know in an hour. I have not a map of the Pacific, but my memory has preserved a very clear recollection of its southern part. The latitude which I obtained yesterday placed New Zealand to the west of Lincoln Island, and the coast of Chile to the east. But between these two countries, there is a distance of at least six thousand miles. It has, therefore, to be determined what point in this great space the island occupies, and this the longitude will give us presently, with a sufficient approximation, I hope."
"Is not the archipelago of the Pomoutous the nearest point to us in latitude?" asked Herbert.
"Yes," replied the engineer, "but the distance which separates us from it is more than twelve hundred miles."
"And that way?" asked Neb, who followed the conversation with extreme interest, pointing to the south.
"That way, nothing," replied Pencroft.
"Nothing, indeed," added the engineer.
"Well, Cyrus," asked the reporter, "if Lincoln Island is not more than two or three thousand miles from New Zealand or Chile?"
"Well," replied the engineer, "instead of building a house we will build a boat, and Master Pencroft shall be put in command--"
"Well then," cried the sailor, "I am quite ready to be captain--as soon as you can make a craft that's able to keep at sea!"
"We shall do it, if it is necessary," replied Cyrus Harding.
But while these men, who really hesitated at nothing, were talking, the hour approached at which the observation was to be made. What Cyrus Harding was to do to ascertain the passage of the sun at the meridian of the island, without an instrument of any sort, Herbert could not guess.
The observers were then about six miles from the Chimneys, not far from that part of the downs in which the engineer had been found after his enigmatical preservation. They halted at this place and prepared for breakfast, for it was half-past eleven. Herbert went for some fresh water from a stream which ran near, and brought it back in a jug, which Neb had provided.
During these preparations Harding arranged everything for his astronomical observation. He chose a clear place on the shore, which the ebbing tide had left perfectly level. This bed of fine sand was as smooth as ice, not a grain out of place. It was of little importance whether it was horizontal or not, and it did not matter much whether the stick six feet high, which was planted there, rose perpendicularly. On the contrary, the engineer inclined it towards the south, that is to say, in the direction of the coast opposite to the sun, for it must not be forgotten that the settlers in Lincoln Island, as the island was situated in the Southern Hemisphere, saw the radiant planet describe its diurnal arc above the northern, and not above the southern horizon.
Herbert now understood how the engineer was going to proceed to ascertain the culmination of the sun, that is to say its passing the meridian of the island or, in other words, determine due south. It was by means of the shadow cast on the sand by the stick, a way which, for want of an instrument, would give him a suitable approach to the result which he wished to obtain.
In fact, the moment when this shadow would reach its minimum of length would be exactly twelve o'clock, and it would be enough to watch the extremity of the shadow, so as to ascertain the instant when, alter having successively diminished, it began to lengthen. By inclining his stick to the side opposite to the sun, Cyrus Harding made the shadow longer, and consequently its modifications would be more easily ascertained. In fact, the longer the needle of a dial is, the more easily can the movement of its point be followed. The shadow of the stick was nothing but the needle of a dial. The moment had come, and Cyrus Harding knelt on the sand, and with little wooden pegs, which he stuck into the sand, he began to mark the successive diminutions of the stick's shadow. His companions, bending over him, watched the operation with extreme interest. The reporter held his chronometer in his hand, ready to tell the hour which it marked when the shadow would be at its shortest. Moreover, as Cyrus Harding was working on the 16th of April, the day on which the true and the average time are identical, the hour given by Gideon Spilett would be the true hour then at Washington, which would simplify the calculation. Meanwhile as the sun slowly advanced, the shadow slowly diminished, and when it appeared to Cyrus Harding that it was beginning to increase, he asked, "What o'clock is it?"
"One minute past five," replied Gideon Spilett directly. They had now only to calculate the operation. Nothing could be easier. It could be seen that there existed, in round numbers, a difference of five hours between the meridian of Washington and that of Lincoln Island, that is to say, it was midday in Lincoln Island when it was already five o'clock in the evening in Washington. Now the sun, in its apparent movement round the earth, traverses one degree in four minutes, or fifteen degrees an hour. Fifteen degrees multiplied by five hours give seventy-five degrees.
Then, since Washington is 77deg 3' 11" as much as to say seventy-seven degrees counted from the meridian of Greenwich which the Americans take for their starting-point for longitudes concurrently with the English--it followed that the island must be situated seventy-seven and seventy-five degrees west of the meridian of Greenwich, that is to say, on the hundred and fifty-second degree of west longitude.
Cyrus Harding announced this result to his companions, and taking into consideration errors of observation, as he had done for the latitude, he believed he could positively affirm that the position of Lincoln Island was between the thirty-fifth and the thirty-seventh parallel, and between the hundred and fiftieth and the hundred and fifty-fifth meridian to the west of the meridian of Greenwich.
The possible fault which he attributed to errors in the observation was, it may be seen, of five degrees on both sides, which, at sixty miles to a degree, would give an error of three hundred miles in latitude and longitude for the exact position.
But this error would not influence the determination which it was necessary to take. It was very evident that Lincoln Island was at such a distance from every country or island that it would be too hazardous to attempt to reach one in a frail boat.
In fact, this calculation placed it at least twelve hundred miles from Tahiti and the islands of the archipelago of the Pomoutous, more than eighteen hundred miles from New Zealand, and more than four thousand five hundred miles from the American coast!
And when Cyrus Harding consulted his memory, he could not remember in any way that such an island occupied, in that part of the Pacific, the situation assigned to Lincoln Island.
第二天4月16日是复活节的星期日，居民们天一亮就从“石窟”里出来，去洗衣服。工程师打算只要找到必要的原料——小苏打或是钾碱，脂肪或是油料——立刻就开始制造肥皂。至于换新衣服，这是一个重要的问题，应该找个适当的时间地点来讨论。他们的衣服很结实，即使体力劳动天天磨损，至少还可以维持六个月，可是一切都要看海岛是不是靠近有人居住的陆地了。如果今天天晴的话，这一点就可以得到解决。
太阳从清晰的水平线上升起来，告诉人们一个晴天到来了。这是一个美丽的秋日，好象温暖季节要离别了，特意给人留个纪念似的。
现在必须测量峭壁的海拔高度，以便完成昨天晚上的观察。
“你不需要一个象昨天晚上用的圆规那样的仪器吗？”赫伯特对工程师说。
“不，孩子，”工程师答道，“我们要换一种方法，只是要做得和昨天一样准确才行。”
只要有机会，赫伯特什么都想学，所以他跟着工程师一起往海滨去了。潘克洛夫、纳布和通讯记者还留在原地做别的工作。
赛勒斯·史密斯准备了一根笔直的木杆，他对自己的身长知道得分毫不差，于是就比比他的身高精确地算出木杆的长度是十二英尺。赫伯特拿着史密斯交给他的垂线，这是用柔韧的植物纤维做成的，一端系着一块石头。他们走到离开海边二十英尺，距垂直的峭壁将近五百英尺的地方，史密斯就小心地把木杆插入沙地二英尺深，他利用垂线使木杆和地面保持垂直。
做完这步，他就后退了一段相当距离，然后趴在沙滩上，在这里眼睛可以同时看到木杆的顶端和峭壁的上沿。他仔细地用一根小棍子在观察点做了一个记号，然后对赫伯特说：
“你知道几何学最基本的原理吗？”
“稍微知道一些，史密斯先生。”赫伯特说，他一点也不想表现自己。
“你记得两个相似三角形应该具备的条件吗？”
“记得，”赫伯特答道，“它们的对应边成比例。”
“好，孩子，我刚做出两个相似的直角三角形，第一个比较小，它的三边是：那根垂直的木杆和从这根小棍子到木杆底部的距离，我的视线就是三角形的斜边，第二个三角形的三边是：垂直的峭壁——我们想测量的也就是它的高度——这根小棍子和峭壁底部之间的距离，和同样是由我的视线所形成的三角形斜边，这斜边也就是第一个三角形斜边的延长线。”
“啊，史密斯先生，我明白了！”赫伯特大声说。“小棍子和木杆之间的距离比小棍子和峭壁底部之间的距离，就等于木杆的高度比峭壁的高度。”
“一点儿也不错，赫伯特，”工程师说，“我们已经知道木杆的长度，再量一下两段水平距离，然后按照比例一算，就可以求出峭壁的高度，省得直接去测量了。”
他们利用木杆量出了两段水平距离，木杆在沙滩上的高度是十英尺整。
第一段距离是从小棍子到插木杆的地方，相距十五英尺。
第二段距离是从小棍子到峭壁底部，相距五百英尺。
量完以后，赛勒斯·史密斯就和少年回“石窟”去了。
工程师拿出一块平板石来，这是他有一次出外打猎的时候带回来的。这块石头就象一块石板，很容易用尖利的贝壳在上面划出字码来。他求出了以下的比例：
15:500＝10:X 500×10＝5000 6000÷15＝333.3
由此得出，花岗石峭壁的高度是三百三十三英尺。
然后赛勒斯·史密斯就把前一天晚上做的仪器拿了出来，圆规两脚之间的距离就是十字架二和水平线之间的角距。他首先把一个圆周分成三百六十等分，然后非常精确地把圆规角度落在圆周上，得出的结果是10度。在这个角度上加上十字架二距离南极的27度，再减去观察的时候所在的峭壁上离海面高度的值，就得出一个37度的角来。南极与水平线之间相距90度，从90度里减去53度还剩下37度。因此，赛勒斯·史密斯测量的结论是：林肯岛在南纬37度线上。如果把计算时不精确的程度估计在内，假设误差有五度，那么海岛的位置一定在南纬35度与40度之间。
现在只等算出经度，就可以确定海岛的位置了。工程师打算就在这天的中午十二点钟，太阳经过子午线的时候进行试验。
他们决定星期日出去旅行，也就是到湖的北边和鲨鱼湾之间那一带去探险。如果时间来得及，他们就继续向南颚角的北边前进。预定在沙丘上吃早饭，直到傍晚再回来。
八点半钟的时候，小队沿着海峡的边缘前进。对面的安全岛上许多飞鸟在大摇大摆地走着。它们的叫声活象驴子，一听就知道是潜水鸟。潘克洛夫只是从吃的观点来看它们。他很满意，因为这种鸟的肉虽然黑一些，吃起来味道却不错。
他们还望见一些巨大的两栖动物在沙地上爬行着，毫无疑问，那是海豹。它们大概是打算在小岛上安家，这种动物是不可能从吃的观点来看的，因为海豹的肉非常油腻，不好吃。可是赛勒斯·史密斯还是很仔细地看着它们，他没有说出自己怎样想，只是告诉大家，不久他们要到小岛上去一次。海滩上散布着无数的贝壳，有的如果让贝壳学家看见了，一定会心花怒放；其中有酸浆贝、三角蛤等等。可是更实惠的是：纳布在退潮的时候，在距离“石窟”将近五英里的岩石丛中发现了一大片蛤蜊场。
“纳布这一天真没有白过。”潘克洛夫看着这一大片的蛤蜊场说。
“这个发现真运气，”通讯记者说，“据说每只蛤蜊每年能产卵五万到六万个，这样我们就永远也吃不完了。”
“我只知道蛤蜊并没有什么营养。”赫伯特说。
“不错，”史密斯说。“蛤蜊里面所含的蛋白质很少，如果一个人成天单吃蛤蜊，那每天至少需要吃十五到十六打才行。”
“好极了！”潘克洛夫说。“我们可以拼命的吃，反正这里的蛤蜊是吃不完的。我们要带一些当早饭吗？”
水手和纳布知道大家一定赞成，不等回答，就捡了一大堆的蛤蜊。他们把蛤蜊装在纳布用木槿纤维做的一只网袋里，跟原来已经装着的其他食物放在一起，然后他们继续爬上沙丘和大海之间的海滨。
史密斯不时地看表，以便准时观察太阳，这项工作必须在正午进行。
海岛的这部分，直到联合湾尽头的南颚角，全都很荒芜。这里什么也看不见，满眼尽是沙石和贝壳，夹杂着一些熔岩的碎片。只有一些海鸟常到这一带荒凉的海岸上来，例如海鸥、巨大的信天翁和野鸭，潘克洛夫对于野鸭非常向往。他想用箭射几只下来，可是没有成功，野鸭难得停下来，他还没有本领在它们飞的时候射中它们。
于是水手又对工程师说：
“你瞧，史密斯先生，如果没有一两支猎枪，我们这辈子也打不到什么东西的！”
“那当然没有疑问，潘克洛夫，”通讯记者说，“可是这要靠你。你给我们找一些铁来做枪身，钢做撞针，硝石、炭和硫磺做火药，水银和硝酸做雷汞，铅做子弹，有了这些，就是最新式的枪，赛勒斯也能给我们做出来。”
“噢！”工程师答道，“肯定地说，岛上是可以找到这些东西的。不过枪的构造非常精致，需要有特殊工具才能制造。我们以后再说吧！”
“那么，”潘克洛夫大声说，“当时我们为什么要把吊篮里所有的武器，所有的用具，连我们的小刀都扔出去呢？”
“假如当时不把它们扔出去，潘克洛夫，气球就要把我们沉到海底下去了！”赫伯特说。
“嗯，你说的也是实话，孩子。”水手说。
然后，水手又想起了别的问题。
“你想，”他说，“约拿旦·福斯特和他的伙伴第二天早上发现人跑了，气球也飞了，一定要急死了！”
“我才不管他们呢。”通讯记者说。
“这都是我的主意！”潘克洛夫得意洋洋他说。
“这个主意真不错，潘克洛夫！”吉丁·史佩莱笑道，“它把我们弄到这儿来了。”
“我宁可在这儿，也不愿意在南方人的手里，”水手大声说，“尤其是史密斯先生又回到我们这里来了。”
“我也这样想，真的！”通讯记者说。“并且，我们还想要什么呢？什么也不缺了。”
“假如不是这样的地方……什么都需要了！”潘克洛夫耸耸肩笑道。“再说，总有一天，我们要想法子离开这儿的！”
“如果林肯岛离开有人居住的海岛或大陆只是一般的距离，”工程师说，“那么，朋友们，这个日子也许会比你们所想的来得早一些。林肯岛的位置一个钟头之内我们就可以知道了。我没有太平洋的地图，可是太平洋南部地理我脑子里记得很清楚。根据昨天我所测出的纬度，林肯岛的西边是新西兰，东边是智利的海岸。可是这两个国家中间相距至少有六千英里。因此，必须肯定这个岛究竟在这一大片海洋中的哪一点，这一点我们马上就可以从经度上知道了，我相信可能相当准确。”
“帕摩图群岛是在同一纬度上离我们最近的地方吗？”赫伯特问道。
“是的，”工程师答道，“可是我们离它还在一千二百英里以上。”
“那边呢？”纳布指着南方，别人的谈话使他很感兴趣。
“那边什么也没有。”潘克洛夫回答说。
“不错，什么也没有。”工程师补充道。
“赛勒斯，”通讯记者问道，“如果林肯岛距离新西兰或是智利不到两三千英里呢？”
“那么，”工程师回答说，“我们就不盖房子，先造船，由潘克洛夫来指挥……”
“好哇，”水手大声说，“我随时准备着当船长——只等你做一只能够航海的船！”
“必要的话，我们就造一只。”赛勒斯·史密斯回答说。
的确，这些人遇事从来也不慌张，他们谈着谈着，观测的时间渐渐地接近了。赫伯特始终猜不出赛勒斯·史密斯不用任何仪器怎么能确定太阳通过海岛子午线的路线。
这时候观测家们离“石窟”大约走了六英里，距工程师在神秘地得救之后而被他们找到的那部分沙丘不远。他们在这里停下来，准备吃饭，这时候已经十一点半了。赫伯特向附近的一条小河跑去，用纳布带来的一只瓶子装了些淡水回来。
在准备吃饭的时候，史密斯把所有的东西都安排好了，打算进行天文观察。他在海滨选了一片开阔的地方，这里落潮以后，地面非常平整。这片细沙地和冰面一样平滑，甚至没有一粒沙子象是摆错了地方。至于地面是不是水平，那倒无关紧要，同时，插在地上的那根六英尺高的标杆是不是和地面垂直，也没有多大关系。相反的，工程师还把它歪向南边，也就是海滨背着太阳的方向，因为有一点必须记住：由于海岛在南半球，所以林肯岛上的居民所看见的太阳运行的弧线不在南边的水平线上，而是在北边。
现在赫伯特明白工程师打算怎样确定太阳的中天，也就是经过海岛子午线的方位了。所谓经过海岛子午线的方位，换句话说，就是当地的正南方。他的方法是测量一根标杆在沙地上的投影，在没有仪器的条件下，这个方法可以使他得到他所想求得的相当准确的结果。
按道理，当影子的长度缩到最短的时候，应该正是中午十二点钟，仔细地看着影子的末端，就可以找出影子在逐渐缩短以后，又开始伸长的一刹那。赛勒斯·史密斯把标杆偏向和太阳相对的方向，就可以使影子长一些，因此它的变化就更加容易看清了。日晷的时针愈长，针点的移动也就愈加容易辨别。标杆的影子也就相当于日晷上的指针。
赛勒斯·史密斯估计时间到了，就跪在沙地上，标杆影子逐渐缩短，他就用小木桩一个一个地随着影子插在地上作为标志。他的伙伴们怀着极大的兴趣，弯着腰注视着工作的进行。通讯记者手里拿着表，随时准备报告影子缩到最短时的时刻。还有一点需要说明，赛勒斯·史密斯进行观测的这天是4月16日，这一天的正式时间和平均时间完全相同，因此吉丁·史佩莱的表上的时间，也就是当时华盛顿的真实时间，这样计算起来就简单了。这时候，随着太阳的移动，影子也逐渐缩短，等赛勒斯·史密斯发现影子开始往回长起来的时候，他就问道，“什么时候？”
“五点零一分。”吉丁·史佩莱马上答道。
他们现在只差把结果计算出来。没有比这个更容易的了。由此可见华盛顿和林肯岛的经差大约是五小时，也就是说，林肯岛中午的时候，华盛顿已经是傍晚五点钟了。太阳环绕地球的视动每过一度需要四分钟，也就是一小时移动15度。15度乘5（小时）等于75度。
华盛顿的经度既然是77度3分11秒，也就是从格林威治子午线——美国和英国都以格林威治为经线的起点——算起的第77度，由此可以算出：海岛一定在格林威治子午线以西77度加75度，也就是西经152度的地方。
赛勒斯·史密斯向伙伴们宣布了这个结果，同时，也象计算纬度时一样，估计了观察时可能发生的误差。他相信他可以肯定林肯岛的位置在纬度35度到40度之间，经度在格林威治子午线以西150到155度之间。
可以看出，在观察中，他估计可能发生的误差是上下五度，一度合六十英里，在实际位置上，经纬线五度可能形成的差错也就是三百英里。
可是这个误差并不影响所要知道的推断。显然林肯岛距离任何一个国家和岛屿都非常远，如果打算乘一只小船到那里去，那未免太冒险了。
根据计算的结果，这个海岛实际上离泰地岛和帕摩图群岛至少有一千二百英里，离新西兰一千八百多英里，和美国的西海岸相距四千五百英里以上!
赛勒斯·史密斯回忆了一下，他想不起在太平洋的这部分有什么岛屿靠近林肯岛。