Well, I mean, primarily throughout the 19th century, it is for as I said, primarily for navigational purposes, and particularly as as a as an aid for the American Merchant Marine and wellfleet as it expands in the 1840s 1850s, to be a really a very significant part of the American economy, and a real the vanguard of American expansionism across the ocean, you know, I really, it's really commercial purposes, it's seeking external markets. It's resource extraction in terms of whales, or in the case of the Fiji Islands, which I read about bass de mer, the sea slug, which is sold in China by Salem merchants out of out of ship and ship owners and masters out of Salem, Massachusetts. And so the Navy's primary role throughout the 19th century as a relatively small force, it's not anything really like the modern US Navy that we know in the 20th century. Its primary objectives are commerce, rating and time of warfare, commerce, protection and time of peace and Coast defense. And and so in in that effort to aid American commerce, American naval science really gains and important footing as the American Merchant Marine and whale fleet become really the second most powerful force and economically powerful force in the world behind Great Britain. And so, so these this is really an effort to understand the, you know, the physical geography of the ocean floor and of ports and coastlines around the world, some of which are quite remote in places like the Fiji's experienced a spike in commercial activity in the 1830s and 1840s. But it was still a really remote place from you know, Europe in from the United States. And its, you know, its harbors were not well charted. And these, you know, the Fiji's and many other Pacific Islands as the United States becomes more oriented towards the Pacific are really dangerous for American mariners to navigate ships are grounding ships are sinking cargoes are lost, human lives are lost. And so this is this is tremendously affecting in a negative way American economic growth. And so that fit nicely within the US Navy's traditional 19th century role of support for American maritime commerce. And so most of this, the surveying and shorting activity, including mores in the 1840s, and 50s, was about helping American mariners get to where they were going to trade to extract resources to find whales more safely, more quickly, more efficiently, and more cheaply. And so they were tremendous commercial motivations here. And the Navy's work, although important always existed, as I said, alongside private efforts, then in some cases, communal or community efforts, such as those that are formalized by the sailor marine society, for example, or their marine societies and many of the ports in the United States in the in the early mid 19th century that are in part about sharing, environmental and navigational knowledge. So that charts can constantly be revised. It was a very, it was a process that was fundamentally rooted in revision it was it sure creating new charts of places that were blank spaces on the map, but but it was also about updating existing charts as more information was found. As as erroneous information was erased, you might imagine, you know, thinking that you're traveling over overseas where you know, you're nowhere close to grounding. And then all of a sudden find yourself high and dry on a on a shoal. So those errors were gradually corrected. And this by the 1850s represented an international effort. It was not just a sort of private public collaborative effort by the Navy and civilian maritime societies and private chart makers like blunt and outage. But it was also an international effort as well, because some little was known about the the contours of the ocean, and even along, you know, commercially important coastlines, such as the Fiji's now, the the importance of hydrography, I think changes over time, so that by the 19th century, when the Navy undergoes this philosophical, intellectual and technological revolution, to create the modern steel and steam powered Navy that would become a world power during and after the Spanish American War in 1898. The importance of hydrography takes on new new aspects. And then they're particularly military and strategic and it becomes it becomes less about commercial presence, although that's never goes away. And then my argument in the book is that it becomes more of a strategic necessity, as the Navy is now compelled to figure out how to defend a far flung oceanic Empire from Germany and the Caribbean or from Japan, in the western Pacific. It's about knowledge of these coastlines that weren't necessary didn't have necessarily commercial value, but they had strategic value. They were really good, perhaps US naval bases, or staging areas for possible naval battle and, you know, mahogany and kind of terms. So I think the value of hydrography for the Navy evolves over the course of the 19th century, you know, generally speaking from commercial interest to strategic and imperial interest, but but we can clearly see, right that there is despite this evolution and change, there is a continuity here, right, that we're talking about different kinds of empire here. All right, that that maritime historians and naval historians have been talking for a long time now about an American commercial Empire in the antebellum era. And that's, in many ways related, but also different from the more formal territorial empire that comes about, really, with 1898. And the acquisition of Guam and the Philippines and Puerto Rico and Hawaii and other places around